01
Your day, modelled
Set your sleep and your coffees. The dashed line is the same day without caffeine — the shaded band between them is the entire contribution of the drug.
alertness · 24 hourstwo-process model · live
Sharpest—
What the coffee bought—
Still on board at bedtime—
Awake at lights-out—
Advanced — how fast you clear caffeine
Half-life is how long your body takes to clear half a dose. At the 5-hour average, a 4pm coffee is still half-present at 9pm and a quarter-present at 2am. Between real people it runs from about 2 to 10 hours — genetics, smoking, pregnancy and the contraceptive pill all move it, and it changes your evening more than almost anything else on this panel. Most people have no idea what theirs is, so pick the description that sounds like you.
Caffeine — drag a cup along the timeline, or use the arrow keys
How many milligrams is a coffee? Less standard than you would hope. Measured across 97 Australian espresso servings the mean was 106 mg, and the range ran from 25 to 214 mg; a second Australian survey of 131 servings in four cities found the same mean and noted big differences within the same brand at different shops. A UK survey found one espresso at 322 mg. ⛔ So a “double shot” is not a unit: 90 mg is a fair default and your actual cup could be half or double that. [130][131][132]
Or start from
This is a model, not a prediction about you.what it does, and what it cannot do (9)
- It runs the two-process model of sleep regulation — a homeostatic pressure that builds while you are awake, against a circadian rhythm that does not care what time you got up — with a standard one-compartment model of caffeine on top.
- The half-life is a control, not a constant. Between real people it ranges from roughly 2 to 10 hours depending on genetics, smoking, pregnancy and hormonal contraception, and that single number changes your evening more than anything else here.
- Caffeine is not added to your alertness. It blocks the receptors that report sleep pressure, so it is drawn as a mask over the pressure rather than a gain on top of it.
- It also blunts sleep inertia, which is why the model registers a 7am cup at all. Even then the larger part of the lift is already pressure-masking: about +1.5 against +2.5 at 07:45, and almost all of it by 09:00.
- Two ordinary cups lift the line you feel back toward a rested day. That is not reassurance, it is the actual danger — the signal being suppressed is the one that would have told you to stop.
- ⛔ It charges nothing for chronic sleep debt. The homeostatic process settles within about two nights, so a short night can plot ABOVE a rested day from early afternoon. That is the model's blind spot, not a finding — and, uncomfortably, it is also exactly the illusion the drug produces in real life.
- A “nights like this” control was built for this panel and then deleted: it moved the curve by almost nothing, and a control that does nothing is decoration pretending to be a model.
- It does not produce the famous post-lunch dip. The classic two-process model simply does not predict one, and later models add it as an explicit extra term.
- The 0–100 scale is a normalisation of the model's output, not a percentage of anything measurable — only the shape and the gaps mean anything.
⚠ Not medical advice — not a doctor
No one involved is a doctor, dietitian or pharmacist. Do not change any medication because of this page.
02
The short version
The conclusions, best first. Each one links to its evidence.
What works, best first
01Sleep: adequate duration and a regular wake timeProtect 7–9 hours and a stable wake time. You cannot supplement your way around this.ESTABLISHEDread more →02Fix a real medical cause before buying a nootropicTest iron, thyroid, B12, sleep apnoea and ADHD before assuming you need a stack.ESTABLISHEDread more →03Stop fragmenting attention: notifications, open tabs, open-plan chatterBatch interruptions. The viral '23 minutes to refocus' number is sloppy; the underlying cost is still real.GOOD EVIDENCEread more →04Morning outdoor light and a stable circadian phaseGet outdoor light in the first hour after waking. A cloudy day still beats a bright office.GOOD EVIDENCEread more →05Treat insomnia with CBT-I, not nightcapsIf you cannot sleep, use CBT-I (sleep restriction + stimulus control). Alcohol is a false friend.ESTABLISHEDread more →06Exercise: a bout today, fitness over monthsA 20–40 min moderate bout lifts attention for hours. Fitness adds a smaller chronic bump.GOOD EVIDENCEread more →07Caffeine used as a tool, not a baselineDelay the first cup, cap the dose, stop 8+ hours before bed. Habitual use mostly treats its own withdrawal.MIXEDread more →08L-theanine with caffeineThe most replicated legal stack: slightly cleaner attention than caffeine alone, small-to-moderate effects on lab tasks.MIXEDread more →What to stop doing
×Do not use alcohol as a sleep aid if tomorrow's focus matters.2025 Sleep Medicine Reviews meta-analysis: REM delayed and reduced from doses ≤0.5 g/kg upward, dose-dependently.HARMFULread more →×Do not stack caffeine + modafinil + amphetamines 'to get more done'.Healthy-volunteer work already shows more effort and sometimes worse solution quality on complex tasks; cardiovascular effects are…HARMFULread more →×Do not take modafinil on hormonal contraception without a non-hormonal backup.CYP3A4 induction; advice is backup contraception during use and for one month after stopping. Separate pregnancy-malformation sign…HARMFULread more →×Do not buy lion's mane, racetams or 'neurofuel' blends as if they were caffeine.See graveyard. Product quality (mycelium-on-grain vs fruiting body; unlisted racetam doses) is an additional failure mode.WEAKER THAN CLAIMEDread more →×Do not microdose psilocybin for productivity in Australia.Szigeti 2021; TGA authorised-prescriber pathway is not a focus indication.HARMFUL-OR-FUTILEread more →Everything below is the working: the evidence, the counterpoints, the things that do not work, and 129 sources. Follow a read more to go straight to one.
03
The perfect day
Hour by hour — and an honest note on why it is a peak day rather than a protocol.
Assuming a 07:00 wake. Every step is drawn from an entry further down this page — nothing in this day is advice that has not already been graded, and each step links to its evidence.
The night before
The day starts here, not at the alarm. Alcohol shortens sleep onset and then fragments the second half of the night and suppresses REM; you pay for it tomorrow and misattribute it.
the evidence →07:00 · Wake
Regularity of timing is the lever, and a stable wake time is what the circadian side of the model is anchored to. A lie-in on the one day you need to perform moves the clock the wrong way.
the evidence →07:15 · Outside
Light is the dominant entraining signal, and the indoor/outdoor gap is typically five- to tenfold — an overcast morning outside still beats a bright room.
the evidence →07:30 · Move
A single session sharpens the next few hours. The effect is honestly SMALL, but it is free, it compounds over months, and it costs nothing on the downside axis.
the evidence →08:30 · First caffeine — deliberately late
Hold the first dose until you have been up a while. Pair it with L-theanine if you have it. [23][24][26][27]
Caffeine works by masking sleep pressure, and at 7am there is barely any to mask. Delaying it puts the dose where it does something. Theanine takes the edge off rather than adding a second engine.
the evidence →09:00–12:00 · The block
One task. Notifications off, phone in another room, no tabs open that are not the task. [8][9][10][11]
This is the largest free lever on the page. You cannot pharmacologically out-run an environment that interrupts you every few minutes, and resuming after an interruption is slow and error-prone.
the evidence →12:30 · Eat, and drink water
Mild dehydration has a small but real attention cost — the direction is agreed even though two competent meta-analyses disagree on the size. Do not worship litres; just do not get dry.
the evidence →13:30 · The dip — nap, do not re-dose
Ten to twenty minutes, alarm set. Or a walk. What you do NOT do is reach for another coffee. [28][29][30]
A short nap discharges real pressure; a second coffee only masks more of it and follows you to bedtime. Keep it under twenty minutes and before mid-afternoon or you pay twice.
the evidence →14:00 · Last caffeine, if any
The half-life is around 5 hours on average and runs to 10 in slow metabolisers, so a mid-afternoon cup is still measurably in you at lights-out. The instrument above will show you your own number.
the evidence →14:00–17:00 · The second block
The model's sharpest window for a 07:00 riser. Put the hardest thinking here, not the email. [3][76]
Circadian drive is climbing while the morning's caffeine is still working. This is the part of the day most people spend on admin.
the evidence →19:00 · Dim, and still no alcohol
Evening light delays the clock you spent the morning anchoring, and alcohol turns a good night into a fragmented one. Morning light matters more than blue-blockers do.
the evidence →23:00 · Bed, same time as always
A perfect day that costs you the night has not worked — it has borrowed. The point of the protocol is to arrive at tomorrow intact.
the evidence →⛔ This is a peak day, not a protocol, and it only works because it is not every day. The caffeine step in particular depends on not being at baseline tolerance — used daily it stops being a tool and becomes the thing you need to feel normal, which is the single most common self-inflicted focus problem there is. Almost everything else here (the sleep, the light, the block, the walk) is genuinely better daily and costs nothing. If you strip this day down to what is worth repeating forever, you are left with: same wake time, get outside, move, defend one block, do not drink, sleep. The rest is what you add on the day it matters.
04
What this page is, and what it is not
- This page is a structured evidence file, not a shopping list and not medical advice.
- It exists because focus advice is usually delivered with more confidence than the trials support.
- Every intervention is scored on four axes — effect, control, enjoyability, downside — and given an evidence grade that distinguishes restoring a deficit from adding a gain.
- Prescription and illegal substances are described as science and law, not as protocols.
- If a marketed claim rests on a three-minute reaction-time task, a deficient sample, or a manufacturer trial that failed to replicate, that is stated.
05
The ladder
Ranked by what they are worth for sustained focus across a working week — not by effect size in a single lab session. An intervention with a large effect and a severe downside cannot hide at the top of this list, because the downside is a column, not a footnote.
01Sleep: adequate duration and a regular wake timeProtect 7–9 hours and a stable wake time. You cannot supplement your way around this.habitESTABLISHED
If you regularly sleep six hours and feel 'fine', you are a poor judge of your own focus. Objective attention keeps falling while the feeling of sleepiness plateaus.
- Van Dongen et al. restricted healthy adults to 4, 6 or 8 hours in bed for 14 days.
- After two weeks, the 6-hour group’s psychomotor vigilance matched one night of total sleep deprivation; the 4-hour group matched two nights.
- Subjective sleepiness flattened after a few days and no longer distinguished 4 from 6 hours.
- Lapses tracked cumulative wake beyond ~15.8 hours per day, near-linearly. [1][2][3]
effectHIGHcontrolMODERATEenjoymentHIGHdownsideNEGLIGIBLE
Legal status n/a
CounterpointShort-sleeper genotypes exist but are rare. Feeling recovered after 6 hours is not evidence you are a short sleeper.
02Fix a real medical cause before buying a nootropicTest iron, thyroid, B12, sleep apnoea and ADHD before assuming you need a stack.habitESTABLISHED
The largest cognitive gains from any 'supplement' in this file come from correcting a deficiency or treating a diagnosis. Treating a non-deficient person does not produce those gains.
- In women of reproductive age, iron repletion after low ferritin produced large improvements on cognitive tasks (Murray-Kolb & Beard: 5–7-fold improvement in a composite when ferritin rose).
- A 2025 meta-analysis in non-anemic menstruating adults found RCTs improved short-term memory (d=0.53) and intelligence measures (d=0.46) only when iron deficiency was present.
- Adult ADHD stimulant evidence is strong; healthy-volunteer enhancement evidence is not. [4][5][6][7]
effectHIGHcontrolHIGHenjoymentHIGHdownsideMINOR
Legal status n/a
CounterpointNot every foggy week is a disease. Over-investigation has its own cost. The point is: do not skip the cheap, high-yield tests.
Do no harmUnnecessary iron can cause GI harm and, rarely, iron overload. Stimulants without a diagnosis carry dependence and cardiovascular risk.
03Stop fragmenting attention: notifications, open tabs, open-plan chatterBatch interruptions. The viral '23 minutes to refocus' number is sloppy; the underlying cost is still real.environmentGOOD EVIDENCE
Every ping does not cost a clean 23 minutes of IQ. What the workplace observation studies actually measured is time until the original work-sphere is resumed — often 20–25 minutes on average, with huge variance — plus faster, more stressed work when people try to compensate.
- Mark, Gonzalez & Harris shadowed knowledge workers: 57% of working-sphere segments were interrupted; same-day resumption averaged ~25 minutes overall and ~23 minutes after external interruptions, SD ~55 minutes.
- The tidy '23:15' figure circulated from interviews more than from a single published cell.
- The 2008 CHI paper found interrupted work was done faster but with more stress and more errors.
- Phone-on-desk 'brain drain' (Ward 2017) failed a pre-registered direct replication. [8][9][10][11]
effectHIGHcontrolHIGHenjoymentMODERATEdownsideNEGLIGIBLE
Legal status n/a
CounterpointSome jobs are interruption-shaped. The lever is batching, not monastic silence.
04Morning outdoor light and a stable circadian phaseGet outdoor light in the first hour after waking. A cloudy day still beats a bright office.habitGOOD EVIDENCE
Your body clock is set by light, not by willpower. Indoor office light is often 300–500 lux. Overcast daylight is several thousand. That gap is why 'I sit by a window' is not the same intervention as going outside.
- Process C in the two-process model is light-entrained.
- The evening wake-maintenance zone (hard to fall asleep 2–3 h before habitual bedtime) and the pre-dawn circadian nadir are robust findings from forced-desynchrony work (Dijk & Czeisler).
- Aligning work to chronotype has observational and some experimental support; it is not horoscope, but the popular version overstates how freely most jobs can move. [3][12][13][14]
effectMODERATEcontrolHIGHenjoymentHIGHdownsideNEGLIGIBLE
Legal status n/a
CounterpointBlue-blocking glasses as a universal evening fix are weaker than blogs claim. Spectrum matters less than intensity and timing.
05Treat insomnia with CBT-I, not nightcapsIf you cannot sleep, use CBT-I (sleep restriction + stimulus control). Alcohol is a false friend.habitESTABLISHED
CBT-I is the first-line treatment for chronic insomnia in guidelines because it changes the behaviour that maintains the problem. Alcohol knocks you out and then wrecks the second half of the night.
A 2024 JAMA Psychiatry component network meta-analysis of 241 trials (n=31,452) found sleep restriction, stimulus control and cognitive restructuring as the active pieces; NNT around 3 versus psychoeducation for the best package. Alcohol meta-analyses show REM delayed and reduced even at ≤0.5 g/kg (~two drinks), with first-half REM cuts of ~9–24% at low-to-moderate doses and worse fragmentation after midnight. [15][16][17]
effectHIGHcontrolMODERATEenjoymentMODERATEdownsideMINOR
Legal status n/a
CounterpointSleep restriction is temporarily unpleasant. That is why enjoy is only MODERATE.
Do no harmSleep restriction can worsen sleepiness in the first week; do not combine with driving if severely sleepy.
06Exercise: a bout today, fitness over monthsA 20–40 min moderate bout lifts attention for hours. Fitness adds a smaller chronic bump.exerciseGOOD EVIDENCE
Exercise is sold as a brain upgrade. The honest size is small-to-moderate on lab tasks after a single session, and modest for chronic fitness in healthy adults. It is still one of the best-value levers because the downside is almost empty and the enjoyability can be high.
- Chang et al. 2012: overall g≈0.10 across 79 acute-exercise studies.
- A 2025 meta-review of 30 meta-analyses (383 unique studies, n=18,347) found mean SMD 0.33 on cognition after acute exercise, largest when tested after the bout (attention SMD 0.37, executive 0.36).
- A 2024 Bayesian analysis in young adults was smaller still (g=0.13).
- BDNF stories are mostly rodent; human peripheral BDNF rises after exercise but linking that to day-long focus is a leap. [18][19][20]
effectSMALLcontrolHIGHenjoymentHIGHdownsideNEGLIGIBLE
Legal status n/a
CounterpointLab tasks ≠ a six-hour writing block. Timing near bedtime can delay sleep in some people. On the acute effect specifically the honest number is SMALL, not moderate: Chang 2012 gives g≈0.10 and a 2024 young-adult Bayesian analysis g=0.13. The 2025 SMD 0.33 is a meta-of-metas and is probably inflated. The high rank here is earned by the downside and enjoyment columns, not by the size of the acute effect.
Do no harmInjury risk if you jump from zero to hero.
07Caffeine used as a tool, not a baselineDelay the first cup, cap the dose, stop 8+ hours before bed. Habitual use mostly treats its own withdrawal.foodMIXED
If you drink coffee every morning, a large part of the 'focus' you feel is the end of overnight withdrawal. In people who do not use caffeine, the same dose mainly speeds the body and can add anxiety that cancels the mental gain.
- Rogers et al. 2013 (n=369) gave 100 then 150 mg after overnight abstinence.
- Medium-high consumers improved alertness and mental tasks; non/low consumers got less mental benefit and more jitter.
- James & Rogers argue that once tolerance to the anti-sleepiness effect is in place, habitual use is approximately net-zero on mental alertness versus sustained abstinence.
- Motor speed still improves.
- Drake 2013: 400 mg six hours before bed cut objectively measured sleep by ~41–60+ minutes, and people often did not notice. [21][22][23][24][25]
effectMODERATEcontrolMODERATEenjoymentHIGHdownsideMINOR
Legal status legal food/drug
CounterpointSleep-deprived or overnight-abstinent users do get a real acute lift. That is not the same as a net gain from years of three coffees a day.
Do no harmAnxiety, reflux, raised heart rate, sleep loss. Half-life doubles on the pill and in late pregnancy; smokers clear it faster.
08L-theanine with caffeineThe most replicated legal stack: slightly cleaner attention than caffeine alone, small-to-moderate effects on lab tasks.supplementMIXED
Adding L-theanine does not turn coffee into modafinil. It modestly improves attention-switching accuracy and takes the edge off jitter for many people.
- Camfield 2014 meta-analysis: combined caffeine+theanine improved Bond-Lader alertness (SMD 0.54 in hour 1, 0.39 in hour 2) and attention-switching accuracy (SMD 0.38 / 0.29).
- Payne 2025 review of 50 RCTs: attention-switching accuracy SMD 0.33 in hour 2; many CIs still include small effects.
- Moderator trends suggest caffeine dose explains much of the attention effect; theanine’s distinctive contribution is smoothness and some accuracy. [26][27]
effectSMALLcontrolHIGHenjoymentHIGHdownsideNEGLIGIBLE
Legal status legal supplement
CounterpointSplit the question and the grade splits with it: versus PLACEBO the attention evidence is good; versus CAFFEINE ALONE it is mixed, and the page's own moderator note says much of the effect tracks the caffeine dose. Examine.com is more cautious than this page was and was right to be. Theanine is better understood as a jitter buffer than as a second engine.
Do no harmGenerally benign. Theanine alone at 200–400 mg is well tolerated in trials.
09A 10–20 minute afternoon nap (not a 45-minute one)If you can nap, 10 minutes pays immediately. 30+ minutes costs sleep inertia first.habitGOOD EVIDENCE
Short afternoon naps improve alertness for a couple of hours after mild sleep restriction. Longer naps help later but you pay a groggy tax on the way out.
- Tietzel & Lack and Brooks & Lack: after a 5-hour night, a 10-min afternoon nap improved alertness and cognitive tasks immediately for ~2.5 h; 20-min naps showed little immediate benefit; 30-min naps impaired performance for up to ~35 min before recovering.
- Under heavier sleep loss, even short naps can carry inertia.
- Coffee-naps (caffeine then a ~20 min nap) have a small supporting literature as a combined tactic. [28][29][30]
effectMODERATEcontrolMODERATEenjoymentHIGHdownsideMINOR
Legal status n/a
CounterpointLate naps can delay night sleep. Not everyone can nap. The 90-minute 'full cycle' rule is a cartoon of sleep architecture.
Do no harmInertia if you overshoot into slow-wave sleep.
10Creatine — mainly if you are plant-based or sleep-deprivedCheap, safe, real in vegetarians and after a bad night; modest-to-absent in rested meat-eaters.supplementCONTEXT-DEPENDENT
Creatine is not a nootropic for everyone. It tops up a buffer the brain already has. People who eat no meat start lower. People who missed a night of sleep are energy-stressed. Those are the groups with the cleaner signals.
- Rae 2003 and later work: vegetarians improved working memory and processing after creatine.
- McMorris and more recent single-dose studies (0.2–0.35 g/kg during sleep deprivation) reduced deterioration on PVT, logic and language speed by on the order of 6–12% versus placebo.
- Prokopidis 2023 memory meta-analysis: benefit concentrated in older adults.
- Omnivorous, well-rested young adults are the weakest cell. [31][32][33][69]
effectSMALLcontrolHIGHenjoymentHIGHdownsideNEGLIGIBLE
Legal status legal supplement
CounterpointA 2023 six-week crossover found minimal cognitive effect in vegetarians AND omnivores, so the vegetarian advantage is no longer a safe headline. The clearest cells are sleep deprivation and older or low-store adults — which is, again, restoring a deficit rather than adding a gain.
Do no harmAvoid in known kidney disease without medical advice.
11Stay hydrated enough that you are not thirstyMild dehydration can nick attention. The famous 2% rule is real-ish and also oversold.habitMIXED
If you have a headache and dry mouth, drink water. Do not build a personality around electrolyte timing.
- Wittbrodt & Millard-Stafford 2018 (33 studies, 280 effect sizes): overall cognitive impairment ES −0.21; attention ES −0.52; worse when body-mass loss >2% (ES −0.28) than ≤2% (ES −0.14).
- Goodman et al. 2019 meta-analysis found no reliable impairment and argued the critical deficit is probably larger than 2%.
- Two competent meta-analyses disagree.
- Effect, if present, is small. [34][35]
effectSMALLcontrolHIGHenjoymentHIGHdownsideNEGLIGIBLE
Legal status n/a
CounterpointMany dehydration studies confound heat, exercise and fluid loss.
Do no harmForced overdrinking is not harmless.
12Meditation / mindfulness — a slow, small attention trainerMonths of practice, small effects on attention, better evidence for anxiety than for 'laser focus'.habitWEAK
Meditation is not a productivity hack. Against waitlists it often wins. Against good active controls the attention effect shrinks or vanishes.
- Goyal et al. 2014 (47 RCTs, n=3515): moderate evidence for anxiety (d=0.38 at 8 weeks) and depression (d=0.30); low evidence of no effect or insufficient evidence on attention.
- Later mindfulness-attention work is mixed and dose-dependent; benefits that survive active controls are usually small.
- This is not futile — it is just not a substitute for sleep. [36]
effectSMALLcontrolMODERATEenjoymentMODERATEdownsideNEGLIGIBLE
Legal status n/a
CounterpointA minority experience increased distress. The marketing of '10 minutes to rewire your brain' is the problem, not sitting still.
Do no harmRare worsening of trauma symptoms in intensive retreats.
13Modafinil / armodafinil in a rested healthy adultReal but task-dependent effects when you are already slept; much larger when you are not. Prescription-only.drugCONTEXT-DEPENDENT
In a sleep-deprived shift worker, modafinil is a wakefulness drug that works. In a well-slept healthy adult it is a modest, patchy enhancer of planning and long boring tasks, with a few signals of worse divergent thinking, and a legal and contraceptive problem attached.
- Battleday & Brem 2015 reviewed 24 studies in healthy non-sleep-deprived adults: basic tests improved executive function more often than attention or memory; complex tasks were more consistently helped; some reports of impaired divergent creativity.
- Roberts 2020 meta-analyses: small domain-specific effects (modafinil memory updating SMD 0.28).
- Bowman 2023 Science Advances: on a complex knapsack task, modafinil, MPH and dextroamphetamine increased time spent and decreased quality of effort versus placebo. [39][40][41][42][43]
effectMODERATEcontrolLOWenjoymentMODERATEdownsideMODERATE
Legal status Schedule 4 prescription-only medicine. Importing without a prescription is illegal. Not PBS-subsidised for 'focus'.
CounterpointThe 2015 review is often cited as 'modafinil is the first safe smart drug'. That sentence outruns the paper, which called for better tests and flagged ethics.
Do no harmHeadache, insomnia, anxiety, rare serious rash including SJS. Induces CYP3A4: hormonal contraception is less reliable during use and for ~1 month after. MHRA: possible ~15% malformation rate with first-trimester exposure vs ~3% background in a small exposed series — avoid in pregnancy. Do not stack with other stimulants casually.
14Nicotine as a cognitive drugReal small-to-moderate acute attention effects in non-deprived people — purchased with dependence.drugGOOD EVIDENCE
Nicotine is one of the few substances that still shows attention benefits after you subtract withdrawal relief. That is exactly why it is a bad daily focus strategy.
- Heishman, Kleykamp & Singleton 2010 meta-analysed 41 placebo-controlled studies in nonsmokers or minimally deprived smokers.
- Significant effects on alerting attention accuracy and RT, orienting RT, short-term episodic memory and working-memory RT; ES 0.16–0.44.
- A later review (Pasetes 2020) found less uniform attention effects and substantial industry affiliation among authors.
- Dependence liability is not debated. [37][38]
effectMODERATEcontrolLOWenjoymentMODERATEdownsideSERIOUS
Legal status Tobacco products legal 18+. Nicotine vaping is tightly restricted; therapeutic nicotine replacement is pharmacy-regulated. Do not import undeclared nicotine.
CounterpointIf the delivery system is cigarettes, the downside column dominates everything else. Even 'just pouches' train a tightly coupled cue-dose loop.
Do no harmDependence, cardiovascular effects, adolescent brain risk. Smoking adds cancer. Combining with other stimulants stacks heart-rate and BP load.
15Amphetamines and methylphenidate without an ADHD diagnosisThey make you try harder and feel sharper. Objective gains in healthy adults are small; risk is not.drugWEAKER THAN CLAIMED
This is the critical counter-intuitive result in the file. Healthy people on Adderall or Ritalin often believe they performed better. On many batteries they did not. On a hard optimisation task they worked longer and produced worse solutions.
- Ilieva, Boland & Farah 2013: adequately powered crossover of mixed amphetamine salts in healthy young adults — no general enhancement across executive function, memory, creativity, IQ or test performance; participants still believed the active capsule helped more.
- Ilieva & Farah 2013: users rate motivational effects (energy, motivation) at least as high as cognitive ones.
- Coghill/Repantis-type reviews and Roberts 2020: MPH small effects on recall (SMD 0.43), sustained attention (0.42), inhibitory control (0.27); d-amphetamine overall null in that meta-analysis.
- In diagnosed ADHD the risk/benefit is a different conversation and the evidence for treating the condition is strong. [7][40][41][44][45]
effectSMALLcontrolLOWenjoymentMODERATEdownsideSERIOUS
Legal status Schedule 8 controlled drugs (dexamfetamine, lisdexamfetamine, methylphenidate). Unauthorised possession, supply or importation is a criminal offence with serious penalties. This page is not a sourcing guide.
CounterpointA subset with low baseline performance or particular genotypes may gain more. That is not a reason to self-prescribe.
Do no harmDependence, insomnia, appetite loss, tachycardia, hypertension, anxiety, crash, psychosis at high dose, diversion. Combined with caffeine or modafinil the cardiovascular arithmetic is additive.
16Psilocybin microdosing for focusWhen expectancy is controlled, the focus effect largely disappears.drugMISLEADING
People who microdose feel better. People who think they microdosed also feel better. That is the finding.
- Szigeti et al. 2021, eLife, n=191 self-blinded citizen-science trial — largest placebo-controlled psychedelic study at the time.
- All psychological outcomes improved in both microdose and placebo groups; no significant between-group differences on accumulative measures.
- Small acute differences were explained by breaking blind (72% correct guesses).
- Macrodoses are a different intervention and are not a focus tool. [46][47][48]
effectNONEcontrolLOWenjoymentMODERATEdownsideMODERATE
Legal status Psilocybin is controlled. From 1 July 2023, authorised psychiatrists may prescribe it only for treatment-resistant depression under the TGA Authorised Prescriber scheme. Recreational use, microdosing and 'focus' use remain illegal.
CounterpointBlinding psychedelics is hard. A perfectly blinded trial might still find a small effect. None has, so far, on the outcomes people buy it for.
Do no harmLegal risk in Australia. Anxiety, misdose into a full trip, possible valvular risk with frequent use, interaction with serotonergic drugs.
06Do this, not thatThe full DO and DON'T lists, evidence-graded — the short version above carries the strongest of each.
The strongest DOs
Ranked by what they are worth across a week of real work, not by effect in one lab session.
The strongest DON'Ts
Where the evidence of harm, or of wasted money, is clearest.
Protect sleep duration and a regular wake time before touching a supplement. [1]
Two weeks of 6-hour nights produced PVT deficits equal to a night awake, while people stopped noticing.
ESTABLISHEDRepletion trials in iron-deficient women show cognitive gains that dwarf typical nootropic effect sizes; effects vanish when you exclude the deficient.
ESTABLISHEDPut the first caffeine dose after you have been awake a while, and put the last one 8+ hours before bed. [23][24]
Drake 2013: 400 mg six hours pre-bed reduced objective sleep. Half-life ~5 h, much longer on oral contraceptives.
GOOD EVIDENCEProcess C is light-entrained; the lux gap between indoors and outdoors is typically five- to ten-fold.
GOOD EVIDENCEObservational work shows long, highly variable resumption delays after interruptions and more stressed, faster, sloppier work.
GOOD EVIDENCEShort naps improve alertness with little inertia; extra afternoon caffeine is the dose most likely to hit sleep.
GOOD EVIDENCEIf insomnia is the actual problem, seek CBT-I. [15]
Component network meta-analysis: sleep restriction + stimulus control + cognitive work, NNT ~3 for the best package.
ESTABLISHEDDo not use alcohol as a sleep aid if tomorrow's focus matters. [16]
2025 Sleep Medicine Reviews meta-analysis: REM delayed and reduced from doses ≤0.5 g/kg upward, dose-dependently.
HARMFULHealthy-volunteer work already shows more effort and sometimes worse solution quality on complex tasks; cardiovascular effects are additive.
HARMFULCYP3A4 induction; advice is backup contraception during use and for one month after stopping. Separate pregnancy-malformation signal.
HARMFULSee graveyard. Product quality (mycelium-on-grain vs fruiting body; unlisted racetam doses) is an additional failure mode.
WEAKER THAN CLAIMEDSzigeti 2021; TGA authorised-prescriber pathway is not a focus indication.
HARMFUL-OR-FUTILESimons et al. and the 2016 FTC Lumosity action: claims of generalisable work/school benefit were not supported.
FUTILEDo not ignore loud snoring, witnessed apnoeas, or crashing in the afternoon as 'just how I am'. [53]
OSA is a common, underdiagnosed cause of sleepiness and inattention in adults.
HARMFULDo not take iron, thyroid hormone, or high-dose B12 without a reason. [5]
Iron meta-analytic benefits disappeared when iron-replete participants were isolated.
CONTEXT-DEPENDENT07CaffeineThe most important single question on this page is whether your daily coffee is a gain or a refund.
Is caffeine a net gain, or just withdrawal relief? [21][22][59][63]
In habitual users, most of the morning lift is reversing overnight withdrawal. In non-users, mental gains are smaller and anxiety often eats them. Motor speed still improves in both groups.
- Rogers, Heatherley, Mullings and Smith (2013) compared medium-high consumers (n=212) with non/low consumers (n=157) after overnight abstinence, then 100 mg plus 150 mg caffeine or placebo.
- Withdrawn high consumers were sleepier and slower by afternoon; caffeine repaired that.
- Non/low consumers got less mental benefit and more jitter, so net alertness barely moved.
- James and Rogers have argued for years that long-term use versus long-term abstinence is approximately a wash on mental alertness once tolerance to the anti-adenosine sleepiness effect is in place.
- This is contested rather than settled — some sleep-restriction and sports literatures still find net effects — but the withdrawal-reversal account is the one marketing never mentions and the trials designed to test it keep supporting.
effectMODERATEcontrolMODERATEenjoymentHIGHdownsideMINOR
CounterpointA first-ever dose, a night-shift, or a genuine sleep-restricted day is not the habitual-user case. Those are real acute gains. Do not use them to advertise a three-coffee habit. [21][22]
Do no harmWithdrawal headache, low mood and fog last 1–3 days if you stop. That cost is part of the habit, not a reason to never stop. [21]
Half-life, genotype, the pill, smoking, pregnancy [24][25][72][73]
Average half-life is about five hours. The real range in healthy adults is roughly 2.5–10 hours, and some states push it further.
- Oral Tmax is typically 30–60 minutes.
- Clearance is mostly CYP1A2.
- Smoking induces CYP1A2 and can cut half-life from ~6 h to ~3.5 h.
- Combined oral contraceptives roughly halve clearance; published half-lives in OC users cluster around 8–11 h.
- Pregnancy, especially late, can stretch half-life to 10–15 h.
- Liver disease slows it.
- CYP1A2*1F and related variants matter more once the enzyme is induced than in a quiet non-smoker.
- This is why 'no coffee after 2 pm' is correct for some people and needlessly early for others.
effectMODERATEcontrolMODERATEenjoymentHIGHdownsideMINOR
CounterpointSelf-identifying as a 'fast metaboliser' from a direct-to-consumer SNP is weaker than watching what 3 pm coffee does to your 11 pm sleep. [24]
Dose-response, inversion into anxiety, afternoon cutoff [23][74]
More is not better. Past a point you buy jitter and buy tomorrow's sleep debt.
- Cognitive studies cluster at 40–300 mg.
- Drake et al. 2013 gave 400 mg at 0, 3 or 6 hours before habitual bedtime in 12 healthy adults.
- All three timings disrupted sleep versus placebo; even the 6-hour dose cut objectively measured total sleep substantially (about 41 minutes in the conservative read, more than an hour in the authors' summary) and people under-reported it.
- That is the origin of the 'six-hour rule'.
- Given a 5-hour half-life, eight to ten hours is a safer personal rule if you are protecting sleep as the main focus lever.
effectMODERATEcontrolMODERATEenjoymentHIGHdownsideMINOR
Counterpointn=12 for Drake. The direction has been replicated in larger sleep-hygiene literatures; the exact minute-count should not be treated as a law of nature. [23]
L-theanine + caffeine, and whether the vehicle matters [26][27]
The stack is real and small. Tea is not magic; energy drinks add a sugar and sleep problem.
- Meta-analyses (Camfield 2014; Payne 2025) find small-to-moderate benefits of theanine-plus-caffeine versus placebo on attention-switching accuracy and some vigilance measures in the first two hours.
- A large share of the attention effect tracks the caffeine dose.
- Coffee’s chlorogenic acids and tea’s theanine/catechins are plausible modifiers of feel, not proven multipliers of six-hour output.
- Energy drinks add sugar (or sweeteners), often taurine, and marketing doses of caffeine that collide with sleep.
- Decaf is not a focus intervention.
- Coffee-naps — caffeine then a ~20 min nap, so the dose peaks as you wake — have supportive but small trials in sleep-restricted adults.
effectSMALLcontrolHIGHenjoymentHIGHdownsideNEGLIGIBLE
Tolerance, cycling, abstinence [21][22]
A week off restores some sensitivity to the alerting effect. Most people use the week off to feel awful and then resume.
- Tolerance to caffeine’s anti-sleepiness effect builds within days of regular use.
- Tolerance to the jitter is slower and incomplete.
- Structured abstinence studies are what James used to argue for net-zero habitual use.
- There is no high-quality trial showing that a popular 'cycle 5 on / 2 off' calendar outperforms simply using less, later.
effectSMALLcontrolMODERATEenjoymentLOWdownsideMINOR
CounterpointIf caffeine is your only remaining pleasure and you sleep well, a modest stable dose is a reasonable trade. The file’s job is to name the trade. [22]
Do no harmWithdrawal is real for 24–72 hours. [21]
Yerba mate, and the one risk that is about temperature rather than the plant [127][128]
Mate is a caffeine delivery system, roughly comparable to coffee. The claim that it gives “smooth energy without the jitters” is testimonial, not tested. The genuine risk attached to it is not the leaf — it is how hot people drink it.
- On focus specifically there is no good evidence that mate outperforms any other caffeine source, and the “no jitters” reputation rests on user report rather than on trials that compared it head to head.
- What is well established sits elsewhere: the IARC evaluation that made headlines about mate was a classification of VERY HOT BEVERAGES — anything above about 65°C — as probably carcinogenic to humans for oesophageal cancer, while coffee and mate at ordinary drinking temperatures were not classifiable at all.
- Traditional mate is drunk near-scalding and through a straight metal straw, which delivers the hot liquid to the back of the throat, and that is the part worth changing.
- Let it cool.
effectMODERATEcontrolMODERATEenjoymentHIGHdownsideMINOR
CounterpointMost of the very-hot-beverage epidemiology comes from populations whose drinking customs differ sharply from Australian or British ones, and a UK Biobank cohort is a useful corrective to reading those risk ratios straight across. The temperature finding is solid; the size of the risk for someone who lets their drink cool is small. [128]
Do no harmThe risk is thermal and it is avoidable for free: drink it warm rather than scalding. This applies to tea and coffee identically — mate is singled out only because it is traditionally drunk hotter.
08Prescription stimulants and wakefulness agentsWhat the trials measured in healthy, slept adults is smaller and stranger than campus folklore.
Modafinil in slept versus sleep-deprived people [39][40][41][42][43][61][62][71]
These are almost two different drugs. In narcolepsy and shift-work sleepiness the benefit is large. In a slept student the benefit is task-dependent and modest.
- Battleday & Brem (2015) is the paper everyone cites.
- They reviewed 24 studies in healthy non-sleep-deprived adults.
- Simple tasks: executive function often up, attention and memory only about half the time, occasional hits to divergent creativity.
- Complex, long tasks: more consistent benefit.
- Mood and side-effect reporting in those labs was mostly mild (headache, insomnia, nausea — also in placebo).
- Later work is less breathless.
- Roberts et al. 2020 found a small memory-updating effect (SMD 0.28) and no sweeping cognitive lift.
- Bowman et al. 2023 put modafinil, methylphenidate and dextroamphetamine against a knapsack optimisation problem: people spent longer, used more steps, and achieved lower value than on placebo.
- Motivation up, quality of effort down.
effectMODERATEcontrolLOWenjoymentMODERATEdownsideMODERATE
Amphetamines and methylphenidate: ADHD versus enhancement [7][40][41][44][45][54][60][70][78]
In ADHD, stimulants are first-line medicine with a large evidence base. In healthy volunteers they change how hard you try more reliably than how well you think.
- Ilieva, Boland and Farah (2013) ran a powered double-blind crossover of mixed amphetamine salts in healthy young adults.
- No general enhancement across a wide battery.
- Participants still rated the active capsule as more enhancing.
- Ilieva and Farah’s survey work found users put energy and motivation at least level with attention.
- Smith and Farah’s earlier review, Coghill-style ADHD reviews, and Roberts 2020 together say: small domain-specific lab effects for MPH (recall, sustained attention, inhibition), weaker or null overall for d-amphetamine in healthy meta-analysis, and a consistent subjective-objective split.
- Long-term non-prescribed use adds insomnia, appetite collapse, dose escalation and dependence.
- That is not a moral statement.
- It is the pharmacology.
effectSMALLcontrolLOWenjoymentMODERATEdownsideSERIOUS
Other wakefulness agents, briefly [40]
Solriamfetol and pitolisant are narcolepsy drugs. Atomoxetine is a non-stimulant ADHD drug. None has a serious healthy-enhancement literature worth building a habit on.
- Solriamfetol (dopamine/noradrenaline reuptake) and pitolisant (H3 antagonist) improve wakefulness in hypersomnia disorders.
- Extrapolating that to a slept knowledge worker is the same error this page exists to stop.
- Atomoxetine can help ADHD; in healthy adults it is more notable for side effects than for focus.
- Do not stack any of these with recreational stimulants.
effectSMALLcontrolLOWenjoymentLOWdownsideMODERATE
CounterpointAbsence of enhancement trials is not proof of absence of effect. It is proof you should not be taking them for that reason.
Do no harmPrescription-only; cardiovascular and psychiatric warnings vary by agent.
09SleepIf this page has a protagonist, it is sleep. Everything else is commentary.
Dose-response, and the night you stop noticing [1][2][75]
Lose sleep and your brain keeps score after your feelings have given up.
- Van Dongen, Maislin, Mullington and Dinges (2003) is the load-bearing study.
- Healthy adults spent 14 days at 4, 6 or 8 hours in bed, plus a total-sleep-deprivation arm.
- PVT lapses accumulated across the fortnight with no adaptation.
- After 14 nights, 6 hours ≈ 24 h awake; 4 hours ≈ 48 h awake.
- Stanford Sleepiness scores jumped early then flattened and could not tell 4 from 6 hours apart.
- A model related lapses to cumulative wake beyond 15.84 h/day (SE 0.73).
- That dissociation — subjective plateau, objective decline — is why 'I only need six' is usually a measurement error, not a phenotype.
effectHIGHcontrolMODERATEenjoymentHIGHdownsideNEGLIGIBLE
Naps, inertia, coffee-naps [28][29][30]
Ten minutes is the high-value nap for a normal afternoon. Thirty minutes is a different drug.
- After a restricted night, Tietzel & Lack and Brooks & Lack mapped 0, 5, 10, 20 and 30 minute afternoon naps.
- Ten minutes: immediate alertness and task gains lasting ~2–2.5 h, little inertia.
- Twenty minutes: benefits delayed ~35 min.
- Thirty minutes: clear inertia, then later recovery.
- Reviews note that under severe sleep loss even short naps can carry inertia because slow-wave pressure is higher.
- A 90-minute nap can include a full NREM–REM cycle and helps learning in some designs, at the cost of more inertia and more risk to that night’s sleep.
- Coffee-nap: caffeine then immediately a short nap so absorption and waking coincide — small supportive literature in sleepy adults.
effectMODERATEcontrolMODERATEenjoymentHIGHdownsideMINOR
CounterpointIf a nap wrecks your night, it was too late or too long. The 'always 90 minutes' rule is folklore. [28][29][30]
Do no harmDriving or operating machinery in the inertia window after a long nap is dangerous. [30]
Timing consistency versus duration, chronotype, light [3][12][13][14][76]
Both matter. A stable wake time is the easier circadian anchor. Chronotype is real; it is not a personality test that rewrites your job.
- Process S cares about duration.
- Process C cares about when.
- Forced-desynchrony work (Dijk & Czeisler) shows why: circadian wake drive peaks in the late evening (wake-maintenance zone, typically 2–3 h before habitual bedtime, ~4–6 h before DLMO on average with wide individual scatter) and sleep propensity peaks near the core-temperature minimum, usually 1–3 h before habitual wake.
- Social jetlag — shifting weekends later — leaves you trying to think on a Monday morning that is still biologically night.
- Morning outdoor light advances the clock; evening bright light delays it.
- Blue-blocker glasses as a standalone intervention have a weaker, more mixed literature than Twitter.
effectMODERATEcontrolMODERATEenjoymentHIGHdownsideNEGLIGIBLE
Alcohol, temperature, CBT-I [15][16][17][64]
Alcohol is the most popular focus-killer that people still describe as self-care.
- A 2025 systematic review and meta-analysis in Sleep Medicine Reviews (27 studies) found delayed REM onset and less REM even at low doses (≤0.5 g/kg), worsening with dose; only high doses reliably shortened sleep latency.
- Serial-night lab work shows more SWS early, less REM early, then fragmentation after midnight as alcohol clears.
- CBT-I remains the evidence-based treatment for chronic insomnia: 241-trial component network meta-analysis, active ingredients sleep restriction and stimulus control plus cognitive work.
- Cool, dark, regular bedtime helps; it does not replace CBT-I when the problem is conditioned arousal.
effectHIGHcontrolHIGHenjoymentMODERATEdownsideMINOR
CounterpointOne drink with dinner is not the same as three drinks as a sleep aid. The REM hit starts lower than people think. [16][17]
Do no harmAlcohol also fragments next-day attention via hangover and residual sedation. [16]
10ExerciseReal, smaller than the brochure, almost uniquely clean on the downside axis.
Acute bout [18][19][20]
After a moderate session, attention and executive tasks run a bit better for a while. Exhaustion is not the same stimulus.
- Chang, Labban, Gapin and Etnier (2012) pooled 79 studies: overall g=0.10, similar during, immediately after, and after a delay.
- The 2025 Psychological Bulletin meta-review (30 systematic reviews, 383 studies, 18,347 people) estimated mean SMD 0.33, largest post-exercise, present across attention, executive function and memory, and surprisingly insensitive to age and exact protocol in that analysis.
- A 2024 Bayesian meta-analysis restricted to young adults was g=0.13.
- Take the range seriously: small, reliable, not transformative.
- Very high intensity can impair in the moment.
effectMODERATEcontrolHIGHenjoymentHIGHdownsideNEGLIGIBLE
Do no harmInjury; late hard sessions can delay sleep in some.
Chronic fitness, BDNF, resistance vs aerobic [18][19]
Fitter people think a bit better on average. The BDNF story is a mechanism poster, not a human dose-response curve.
- Cardiorespiratory fitness associates with better executive function and hippocampal volume in observational and some intervention work, with larger effects in children and older adults than in healthy 25-year-olds already near ceiling.
- Resistance training has its own small executive-function literature.
- Peripheral BDNF rises after exercise in humans; claiming that a particular protocol 'releases BDNF' as if that were the outcome is rodent-to-human overreach.
effectSMALLcontrolMODERATEenjoymentHIGHdownsideNEGLIGIBLE
CounterpointReverse causation and residual confounding sit inside every fitness-cognition cohort. [19]
11Diet, metabolism and deficienciesThe highest-value 'supplement' on this page is a blood test.
Glucose, the post-lunch dip, fasting and ketosis [1][12]
Huge lunches make some people useless. That is not the same as 'blood sugar crash' as a universal law.
- The afternoon dip is substantially circadian (Process C) plus sleep pressure.
- Meal size and high-GI loads can add sleepiness in some people; CGM studies show large inter-individual differences and do not support a single crash narrative in healthy adults.
- Acute fasting can sharpen or dull depending on habit, caffeine, and whether you are still adapting.
- Steady-state ketogenic cognition evidence in healthy young adults is thin; much of the positive literature is epilepsy, older adults, or the first-week adaptation fog everyone forgets to mention.
effectSMALLcontrolMODERATEenjoymentMODERATEdownsideMINOR
CounterpointIf your CGM and your afternoon are obviously coupled, eat differently. Do not generalise your pancreas to the species.
Do no harmAggressive fasting plus hard physical work plus stimulants is a syncope and sleep-debt machine.
Hydration [34][35]
Do not get very dry. Do not worship 3 litres.
- Wittbrodt & Millard-Stafford 2018: small overall cognitive cost of dehydration (ES −0.21), larger for attention (ES −0.52), larger above 2% body-mass loss.
- Goodman et al. 2019: no reliable effect, and they argue the 2% threshold is oversold.
- Grade MIXED because two competent syntheses disagree.
- Practical translation: drink when thirsty, more in heat; ignore branded hydration theatre.
effectSMALLcontrolHIGHenjoymentHIGHdownsideNEGLIGIBLE
CounterpointHeat-plus-exercise protocols inflate the apparent cognitive cost of 'just being a bit dry at a desk'. [35]
Do no harmWater intoxication is a real if rare way to harm yourself in the name of wellness. [34]
Iron, B12, vitamin D, folate, magnesium, iodine, thyroid [4][5][6]
These wreck focus when they are low. They do approximately nothing extra when they are fine.
- Iron/ferritin: the standout.
- Common in menstruating women; non-anemic iron deficiency still associates with fatigue and cognitive cost; repletion improves memory and some intelligence measures (d≈0.5 in 2025 RCT meta-analysis) and produced large task gains in Murray-Kolb & Beard when ferritin rose.
- Test ferritin, Hb, and in some cases transferrin saturation.
- B12: test if vegan, post-bariatric, on metformin or PPI, or older; correction of deficiency restores.
- Vitamin D: deficiency is common; cognitive RCTs in replete adults are disappointing.
- Folate: relevant in deficiency and in pregnancy, not as a nootropic.
- Magnesium: deficiency can disturb sleep; extra magnesium in replete adults is not a focus drug.
- Iodine: deficiency still exists in some regions and wrecks via thyroid.
- Thyroid: hypothyroid brain fog is real; do not start thyroxine as a lifestyle drug.
effectHIGHcontrolHIGHenjoymentHIGHdownsideMINOR
CounterpointReference ranges and 'optimal' influencer ranges are not the same thing. Treat the person and the assay, not the podcast. [5]
Do no harmIron tablets without deficiency; excess iodine; unsupervised thyroid hormone. [5]
Omega-3, creatine, choline, tyrosine, adaptogens, racetams [31][32][55][56]
A few have a conditional signal. Most have a shopfront.
- Omega-3: strongest cognitive signals in older adults with low DHA and in early cognitive decline; healthy young omnivores are a weak cell.
- Creatine: vegetarians and sleep deprivation, as above.
- Choline/alpha-GPC: precursor logic plus a thin, often industry-touched human literature; alpha-GPC has had regulatory scrutiny overseas.
- Tyrosine: the honest case is acute stress plus catecholamine depletion (cold, sleep loss, load), not a daily capsule at a desk.
- Rhodiola, ashwagandha: better evidence for stress/fatigue than for attention per se; ashwagandha has emerging safety flags (liver) that marketing pages omit.
- Bacopa: modest delayed-recall signal after 12+ weeks at ~300 mg standardised extract in small trials; attention results inconsistent.
- Ginkgo: GEM trial (n≈3069, 6 years, 240 mg EGb 761) did not prevent dementia or slow decline in older adults.
- Racetams: not approved medicines in Australia; healthy-adult evidence is poor.
effectSMALLcontrolMODERATEenjoymentMODERATEdownsideMINOR
CounterpointBacopa and creatine are the least embarrassing items in this drawer. That is a low bar. [31][55]
Do no harmAshwagandha hepatotoxicity reports; ginkgo and bleeding risk with anticoagulants; racetam legal status. [55]
12Mushrooms — legal and illegal, kept apartLion's mane is a thin human literature wearing a thick marketing coat. Microdosing is an expectancy story.
Lion's mane, reishi, cordyceps, chaga [49][50]
The NGF/hericenone story is interesting biochemistry. The human trials are small, mixed, and often in older or impaired samples.
- Mori 2009: 30 older Japanese adults with MCI, 750 mg/day powdered fruiting body, 16 weeks, better Hasegawa scores than placebo, scores drifted back after a 4-week washout.
- Docherty 2023: young healthy adults, 1.8 g/day, faster Stroop at 60 minutes acutely; at 28 days delayed word recall was worse than placebo — an under-quoted cell.
- Other culinary-medicinal mushrooms (reishi, cordyceps, chaga) have essentially no convincing healthy-adult focus RCTs.
- Product quality is a separate scandal: mycelium-on-grain can be mostly starch; fruiting-body extracts are what most positive trials used.
effectSMALLcontrolLOWenjoymentMODERATEdownsideMINOR
Do no harmGI upset; rare allergy; quality roulette. [50]
Psilocybin microdosing [46][47][48]
Expectancy survived contact with placebo. The effect did not.
- Szigeti et al. 2021 enrolled 191 people who already intended to microdose, taught them to self-blind, and ran four weeks.
- LSD or analogues were more common than psilocybin in the sample.
- Both arms improved from baseline.
- Between-group accumulative outcomes were not significant.
- Acute 'I feel it' differences tracked breaking blind.
- Later commentaries by the same group sharpened the point: imperfect blinding plus positive expectancy can manufacture the exact anecdotes the internet runs on.
- Macrodose-assisted therapy is a psychiatric research programme.
- It is not a focus intervention and is not legal for that purpose in Australia.
effectNONEcontrolLOWenjoymentMODERATEdownsideMODERATE
CounterpointCitizen-science doses were unverified. A hospital-grade, perfectly blinded trial could still find a sliver. The sliver is not what is being sold. [46]
13Habits, environment and attention hygieneThe environment is a stimulant. Most people take it in the chaotic direction.
Interruptions and the 23-minute figure [8][9]
The number is sloppier than its reputation. The phenomenon is not.
- Mark, Gonzalez and Harris followed real office workers.
- Working spheres were short. 57% were interrupted.
- When work resumed the same day, mean delay was about 25 minutes (external interruptions closer to 23; self-interruptions closer to 29), with a standard deviation near 55 minutes — meaning the average is a poor description of any given ping.
- The viral '23 minutes and 15 seconds to recover full focus' is best treated as an interview rounding of resumption time, not as a stopwatch measurement of deep-work return.
- The 2008 CHI experiment found interrupted work was completed faster, with more stress and more effort.
- Unfinished tasks also leave an attention residue (Leroy).
effectHIGHcontrolHIGHenjoymentMODERATEdownsideNEGLIGIBLE
Phones, music, open-plan noise [10][11]
Notifications are the reliable toxin. Mere presence of a silent phone is a shakier finding than its press cycle.
- Ward et al. 2017 reported worse operation-span performance when a phone was on the desk versus in another room.
- Ruiz Pardo & Minda 2022 pre-registered a direct replication of experiment 2 with location and power manipulated: no location effect on OSpan or go/no-go.
- FORRT currently logs failed replications.
- That does not make phones harmless — the notification and the pick-up are the obvious mechanism.
- Music: instrumental is less competing than lyrics for verbal work; evidence is mixed and task-dependent.
- Open-plan noise impairs complex work more than simple work; that literature is older than startups and still correct.
effectMODERATEcontrolHIGHenjoymentMODERATEdownsideNEGLIGIBLE
Pomodoro, time-blocking, the 90-minute ultradian claim [8]
Timers help some people start. They are not a law of the nervous system.
- Pomodoro (25/5) has almost no serious RCT literature as a named method.
- What it has is a plausible mechanism: a start cue, a permission to stop, and a break before the next block.
- Time-blocking is a planning tactic, not a biomarker.
- The '90-minute basic rest-activity cycle' popularised from Kleitman is a real idea with weak evidence as a prescription for knowledge work; sleep NREM–REM cycles are ~90 minutes, daytime ultradian rhythms are noisier and not a mandate to stand up on the 87th minute.
effectSMALLcontrolHIGHenjoymentMODERATEdownsideNEGLIGIBLE
CounterpointIf a timer gets you through resistance, keep the timer. Do not cite BRAC as the reason.
Meditation, brain-training, nature, cold, breathwork, sauna [36][51][52]
Nature walks and breaks are cheap and under-sold. Commercial brain-training is over-sold. Cold plunges are a mood story wearing a focus badge.
- Meditation: see ladder — small, slow, better for distress than for attention against active controls (Goyal 2014).
- Brain-training games: you improve on the trained task; far transfer to work is the claim the FTC punished Lumosity for making.
- Nature exposure and walking breaks have a modest attention-restoration literature (better than rumination at the desk).
- Cold exposure and deliberate hyperventilation reliably change autonomic state and subjective alertness for minutes; they do not have a serious sustained-focus RCT record in healthy adults.
- Sauna is a cardiovascular and possibly longevity topic, not a focus protocol.
effectSMALLcontrolMODERATEenjoymentMODERATEdownsideMINOR
CounterpointA cold shower that reliably starts your day is a habit with high control and high enjoy for some people. That is not the same as an evidence grade of ESTABLISHED for sustained focus. [36][51]
Do no harmCold water and unsupervised breath-holds have drowned people. This is not rhetorical.
Alcohol and cannabis, next day [16]
Both borrow focus from tomorrow.
- Alcohol: architecture hit the same night, residual sedation and hangover cognition the next day.
- Cannabis: next-day effects depend on dose, THC content, and whether you still have a measurable level in the morning; residual attention and memory costs are documented after heavier use and in regular users, with mixed findings after a single modest evening dose.
- Neither is a focus tool.
effectNEGATIVEcontrolLOWenjoymentMODERATEdownsideMODERATE
CounterpointA single drink with lunch is not a cannabis hangover. Dose still exists. [16]
14Age, stacking, and the things this page is notThe right answer at 22, 45 and 72 is not the same answer.
How the answers move across a life [1][5][19]
Young adults have more spare cognitive capacity and worse sleep habits. Midlife adds iron, apnoea, alcohol and perimenopause. Older adults have a different supplement evidence base.
- Healthy 20-year-olds are near ceiling on many lab tests — which is why enhancement trials look so small.
- The same person at 50 may be iron-depleted, sleeping 6 hours, drinking nightly, and calling it 'just getting older'.
- Omega-3, bacopa and exercise literatures get more interesting after 60, which is not a reason to copy an ageing-trial stack at 28.
- Perimenopause can present as sudden attentional chaos; that is hormones and sleep, not a racetam deficiency.
effectMODERATEcontrolMODERATEenjoymentMODERATEdownsideNEGLIGIBLE
Stacks and the cardiovascular arithmetic [24][41][42]
Combining two mild stimulants does not make a smart drug. It makes a louder heart.
- Caffeine plus nicotine plus a prescription stimulant plus modafinil is a stack that exists in the wild and almost nowhere as a planned trial. Expected effects: more wakefulness, more anxiety, more insomnia, higher heart rate and blood pressure, and a subjective sense of productivity that Bowman-style tasks suggest can decouple from output quality.
- Fluvoxamine and other CYP1A2 inhibitors turn a normal coffee into an overdose.
- Modafinil plus the pill is an unintended-pregnancy stack.
effectMODERATEcontrolLOWenjoymentLOWdownsideSERIOUS
15The graveyardSold hard, tested properly, found approximately empty in healthy adults. Knowing what not to buy is worth as much as knowing what to.
Sold as: Stimulates NGF, grows neurons, upgrades focus.
WEAKER THAN CLAIMEDWhat trials show
Small mixed human trials; one young-adult RCT improved acute Stroop and worsened delayed recall at 28 days. MCI trial signal faded after washout. Mycelium-on-grain products often are not what was studied.
Sold as: The original memory herb.
FUTILEWhat trials show
GEM: 3069 adults 75+, 240 mg EGb 761, median 6.1 years — no reduction in dementia, no slowing of decline. Healthy-adult attention evidence is weak.
Psilocybin microdosing [46]
Sold as: Sub-perceptual doses unlock focus and creativity.
MISLEADINGWhat trials show
Largest placebo-controlled study: placebo improved too; between-group accumulative effects vanished; remaining blips tracked broken blinds.
Racetams (piracetam, aniracetam, phenylpiracetam) [56]
Sold as: The original nootropics.
WEAKWhat trials show
Not registered medicines for this use in Australia. Healthy-adult focus evidence is poor and old. Importation can be a legal problem.
Sold as: Train the brain like a muscle; benefits transfer to work and school.
FUTILEWhat trials show
You get better at the games. Far transfer failed the evidence test hard enough for an FTC deceptive-advertising action.
Blue-blocker glasses as a focus/sleep panacea [14]
Sold as: Block evening blue light, sleep like a farmer.
WEAKER THAN CLAIMEDWhat trials show
Light intensity and timing dominate spectrum tricks. Dedicated blue-blocker RCTs are small and mixed. Not harmful; not the lever.
The 90-minute ultradian work cycle [8]
Sold as: The brain naturally peaks every 90 minutes; work in those cycles.
MISLEADINGWhat trials show
Sleep cycles are ~90 min. Daytime BRAC as a productivity law is a telephone-game version of Kleitman.
Pomodoro as a scientifically validated focus protocol [8]
Sold as: 25/5 is the evidence-based unit of attention.
WEAKWhat trials show
It is a kitchen timer with a good UX. Almost no method-specific RCT base.
Sold as: A silent phone on the desk drains working memory.
MIXEDWhat trials show
The 2017 finding did not survive a pre-registered direct replication. ⚠ This row is about MERE PRESENCE only — notifications and actual interruptions remain one of the largest and best-supported effects on this page, and nothing here softens that.
High-dose vitamin B complexes for energy and focus [5]
Sold as: B vitamins = brain fuel.
CONTEXT-DEPENDENTWhat trials show
Correction of deficiency matters (especially B12). Extra B vitamins in a replete omnivore are expensive urine.
Reishi, cordyceps, chaga for laser focus [50]
Sold as: Functional mushrooms, therefore cognition.
FUTILEWhat trials show
Essentially no adequate healthy-adult focus RCTs.
Tyrosine as a daily nootropic [56]
Sold as: Dopamine precursor, therefore motivation.
EXTRAPOLATEDWhat trials show
The supporting trials are acute stress and depletion designs, not months at a keyboard.
Alpha-GPC / CDP-choline as must-stack choline [56]
Sold as: Raises acetylcholine, sharpens mind.
WEAKWhat trials show
Thin healthy-adult literature; some regulatory concern overseas about alpha-GPC quality and long-term signals. Not ESTABLISHED.
Ashwagandha as a focus adaptogen [56]
Sold as: Lowers cortisol, therefore clearer mind.
WEAKER THAN CLAIMEDWhat trials show
Better data for anxiety/sleep than for attention. Emerging liver-injury reports. Not a focus drug.
Omega-3 for a well-fed 30-year-old's attention [56]
Sold as: Fish oil is brain oil.
EXTRAPOLATEDWhat trials show
Signals cluster in low-DHA older adults and cognitive-decline samples. Healthy young omnivores: weak.
Nootropic pouches sold as a focus product — Ultra (takeultra.com) as the worked example [129]
Sold as: “Razor-sharp focus, calm energy and enhanced mental clarity” from “6 clinically-studied nootropics”, delivered in a pouch.
WEAKWhat trials show
- The product page names two of the six — Enfinity paraxanthine and Alpha-GPC — and publishes NO PER-INGREDIENT DOSE for any of them.
- That single fact settles it without any argument about the ingredients: “clinically studied” refers to studies run at particular doses, so a product that does not say how much it contains cannot be matched to the studies it is invoking.
- This page's own rule applies unchanged — if the dose is hidden, the evidence cannot be applied to the product.
- On the ingredients that ARE named: Alpha-GPC is graded WEAK here for healthy adults, because its better trials are in older and cognitively impaired samples; paraxanthine is a caffeine metabolite whose independent human evidence is thin.
- The companion Energy pouch is more honest, stating 180 mg of caffeine with L-theanine — which is a strong cup of coffee and a supplement this page already grades MIXED.
16Checked against Examine.comEvery compound checked against the best-known independent supplement reference. Where we disagree, the disagreement and the reason are printed rather than resolved quietly.
Here WEAKER THAN CLAIMED Examine Mechanism pages emphasise NGF/hericenones in cells and mice. Study feed: Mori-style MCI signal; 'lion’s mane may not improve cognitive function among young adults'; 2025 single-dose crossover in 18 healthy young adults — no effect on cognition or mood. They list it among brain-health ingredients of interest, which is a catalogue statement, not a strong cognition grade.
Who is right Both. Pass 1 already had Docherty 2023 (acute Stroop up, 28-day delayed recall down). Examine's 2025 single-dose null is a paper pass 1 did not have and should be added. Neither source supports the shopfront claim.
we agreeWho is right Both. Pass 1 already had Docherty 2023 (acute Stroop up, 28-day delayed recall down). Examine's 2025 single-dose null is a paper pass 1 did not have and should be added. Neither source supports the shopfront claim.
Here GOOD EVIDENCE Examine Combining L-theanine with caffeine may blunt caffeine's BP and sleep disruption and 'potentially enhance' attention; 'not all studies have found this synergistic effect'; dose-response lacking; studies small. April 2026 study summary: in 20 athletes, caffeine+theanine was no better than caffeine alone for a coordination/cognition test.
Who is right Examine is slightly more careful and I should move the stack from GOOD EVIDENCE toward MIXED or keep GOOD EVIDENCE only versus placebo, not versus caffeine. Camfield/Payne still support a small add-on; Tuncer 2026 and Examine's own caveat mean 'synergy' is the overclaim, not 'does anything'.
Examine is more negativeWho is right Examine is slightly more careful and I should move the stack from GOOD EVIDENCE toward MIXED or keep GOOD EVIDENCE only versus placebo, not versus caffeine. Camfield/Payne still support a small add-on; Tuncer 2026 and Examine's own caveat mean 'synergy' is the overclaim, not 'does anything'.
Here MIXED Examine Treats caffeine as a core brain-health ingredient. Separate 2023 summary of a 10-day daily-caffeine crossover: sustained 450 mg/day associated with more errors and slower working-memory RT than sustained abstinence — the opposite of the acute story.
Who is right Agreement on the acute-versus-habitual split. That 10-day working-memory worsening is extra weight for withdrawal-reversal / net-zero habitual use and should be cited next to Rogers 2013.
we agreeWho is right Agreement on the acute-versus-habitual split. That 10-day working-memory worsening is extra weight for withdrawal-reversal / net-zero habitual use and should be cited next to Rogers 2013.
Here CONTEXT-DEPENDENT Examine Main-benefits FAQ: may reduce mental fatigue in sleep deprivation or exhaustion; may improve some memory, especially in people with lower baseline stores (older adults); 'more research is needed before creatine can be said to be effective for cognitive performance.' A 2023 crossover summary: 5 g/day × 6 weeks, minimal effect in both vegetarians and omnivores on RAPM and backward digit span.
Who is right Both. The vegetarian exception is weaker than pass 1 implied once you include the 2023 null crossover. Keep CONTEXT-DEPENDENT; narrow the vegetarian sentence.
we agreeWho is right Both. The vegetarian exception is weaker than pass 1 implied once you include the 2023 null crossover. Keep CONTEXT-DEPENDENT; narrow the vegetarian sentence.
Here EXTRAPOLATED Examine Large trial counts on their cognition and memory outcome pages. FAQ on MCI: current evidence does not support supplements including omega-3 for improving cognition or preventing dementia. Alzheimer's FAQ: overall little-to-no benefit for omega-3s in established AD.
Who is right Pass 1's EXTRAPOLATED for healthy young omnivores is the right grade. Examine's raw study counts look more generous than their own FAQ prose. Trust the FAQ.
we agreeWho is right Pass 1's EXTRAPOLATED for healthy young omnivores is the right grade. Examine's raw study counts look more generous than their own FAQ prose. Trust the FAQ.
Here WEAKER THAN CLAIMED Examine Memory outcome table: grade A, 'Moderate Improvement', 6 studies, n=366. Cognition table: grade C, small improvement, 1 study. That split is the tell — memory trials are often stress/anxiety samples, not healthy-desk attention.
Who is right I am more right for this page's outcome. Examine's A-for-memory collapses anxious/stressed samples into 'memory'. Pass 1 graded attention/focus and flagged liver reports. Keep WEAKER THAN CLAIMED for sustained focus; acknowledge a better anxiety/sleep case.
Examine is more positiveWho is right I am more right for this page's outcome. Examine's A-for-memory collapses anxious/stressed samples into 'memory'. Pass 1 graded attention/focus and flagged liver reports. Keep WEAKER THAN CLAIMED for sustained focus; acknowledge a better anxiety/sleep case.
Tyrosine [121]
Here EXTRAPOLATED Examine Memory table lists L-tyrosine as 1 study, n=11. They treat it as a stress-depletion compound in research breakdowns, not a daily nootropic.
Who is right Both. The supporting trials remain cold/load/sleep-loss designs.
we agreeWho is right Both. The supporting trials remain cold/load/sleep-loss designs.
Here WEAK Examine Cognition table: Alpha-GPC grade B, small improvement, 4 studies, n=350 — largely older/impaired samples. CDP-choline appears on the memory table with 2 studies. Brain-health FAQ lists alpha-GPC as an ingredient 'of most interest', which is not the same as 'works in healthy 30-year-olds'.
Who is right Pass 1 is right for the healthy-adult use-case this page is about. Examine's B grade is populated by dementia-adjacent trials. Name that population split on the page.
Examine is more positiveWho is right Pass 1 is right for the healthy-adult use-case this page is about. Examine's B grade is populated by dementia-adjacent trials. Name that population split on the page.
Here FUTILE Examine Supplement page: evidence grade B for cognition among many outcomes; prose says it 'may boost cognition in older populations, particularly in people with dementia.' GEM-sized prevention is not their headline.
Who is right Pass 1 is right for healthy adults and for dementia prevention (GEM + ancillary decline analysis). Examine's B reflects small older/dementia trials and should not be copy-pasted onto a 28-year-old.
Examine is more positiveWho is right Pass 1 is right for healthy adults and for dementia prevention (GEM + ancillary decline analysis). Examine's B reflects small older/dementia trials and should not be copy-pasted onto a 28-year-old.
Here WEAKER THAN CLAIMED Examine Memory table: grade B, small improvement, 11 studies, n=645. Matches the delayed-recall-after-12-weeks story. They note combination trials are mixed.
Who is right Close. Examine's B-for-memory is fair for delayed recall. Pass 1 used WEAKER THAN CLAIMED because marketers sell 'focus' and the attention/speed data are messy. Split the grade on the page: SMALL / GOOD EVIDENCE for delayed recall after ≥12 weeks; WEAKER THAN CLAIMED for acute focus.
Examine is more positiveWho is right Close. Examine's B-for-memory is fair for delayed recall. Pass 1 used WEAKER THAN CLAIMED because marketers sell 'focus' and the attention/speed data are messy. Split the grade on the page: SMALL / GOOD EVIDENCE for delayed recall after ≥12 weeks; WEAKER THAN CLAIMED for acute focus.
Rhodiola [56]
Here WEAKER THAN CLAIMED Examine Not a headline cognition-table winner in the public snapshot. Treated more as fatigue/stress. That is closer to pass 1 than to Reddit.
Who is right Both. Fatigue ≠ six-hour attention.
we agreeWho is right Both. Fatigue ≠ six-hour attention.
Here CONTEXT-DEPENDENT Examine Brain-health FAQ: maintain iodine, zinc, copper, B1, B3, B12, folate; supplement if intake is insufficient. MCI/AD FAQs: B vitamins have little-to-no benefit for improving cognition or preventing dementia in the tested samples.
Who is right Both. Deficiency correction vs replete extra is the whole game.
we agreeWho is right Both. Deficiency correction vs replete extra is the whole game.
Here ESTABLISHED (when deficient) / CONTEXT-DEPENDENT otherwise Examine Memory table lists iron with 5 studies, n=718 — they grade the outcome, not the deficiency split, on the public table. Their broader nutrition stance is 'replete the deficit'.
Who is right Pass 1 is more explicit about the deficiency gate, which is the load-bearing fact. Keep it louder than Examine's table.
we agreeWho is right Pass 1 is more explicit about the deficiency gate, which is the load-bearing fact. Keep it louder than Examine's table.
Vitamin D [119]
Here CONTEXT-DEPENDENT Examine Memory table: many participants across 12 studies. MCI FAQ: evidence does not support vitamin D for improving cognition or preventing dementia. AD FAQ: one supportive AD trial amid a generally thin causal story.
Who is right Both. Replete adults should not expect a focus gain.
we agreeWho is right Both. Replete adults should not expect a focus gain.
Vitamin B12 [125]
Here CONTEXT-DEPENDENT Examine Listed as a nutrient to keep adequate; not sold as a healthy-omnivore nootropic on their FAQs.
Who is right Both.
we agreeWho is right Both.
Magnesium [56]
Here CONTEXT-DEPENDENT Examine Not a top cognition-table entry. Sleep/constipation/deficiency story is stronger than focus.
Who is right Both. Pass 1 already refused to make it a focus drug.
we agreeWho is right Both. Pass 1 already refused to make it a focus drug.
17The fringeThe weird end of focus advice, held to the same standard as the rest. Some of it is real, some is empty, and one of them will damage your eyes.
●Blue-blocker glasses as mysticismOptional accessory. Not a focus intervention.lightWEAKER THAN CLAIMED
Claimed: Amber lenses at dusk 'restore ancestral circadian health' and therefore focus.
Unchanged from pass 1: spectrum tricks are weaker than intensity and timing. The fringe costume (ancestral, pineal, 'blue light toxins') adds no extra evidence. [14]
effectSMALLcontrolHIGHenjoymentMODERATEdownsideNEGLIGIBLE
Real mechanism underneath? Dim evenings help. Cheap dimmers beat expensive orange glasses for most people.
Legal status n/a
●SAD lamps and dawn simulators used off-seasonUse a box if you have winter depression or cannot get outside. Otherwise open a door.lightCONTEXT-DEPENDENT
Claimed: A 10,000-lux box will upgrade winter and summer focus alike.
- Bright-light therapy is ESTABLISHED for seasonal affective disorder and has a role in circadian phase-shifting.
- For a non-seasonal, well-slept person already getting outdoor morning light, extra box time is a weak add.
- Dawn simulators have a smaller, mixed literature for sleep inertia.
- The fringe framing ('biohack your mitochondria with photons') outruns the psychiatry evidence. [14][84]
effectSMALLcontrolHIGHenjoymentMODERATEdownsideMINOR
Real mechanism underneath? Retinal melanopsin → SCN. Same mechanism as going outside. Intensity and timing, not brand.
Legal status Consumer devices.
Do no harmMania risk in bipolar disorder; eye conditions need advice. Do not use as sun-gazing.
●Sun gazingDo not look at the sun. Walk outside in the morning instead.lightHARMFUL
Claimed: Staring at the rising or setting sun (sometimes mid-day) 'charges' the pineal gland, resets circadian rhythm, and upgrades focus without glasses or sunglasses.
- There is no ophthalmology or circadian trial showing a focus benefit from looking at the solar disk.
- There is a large case literature of solar retinopathy: photochemical injury to foveal photoreceptors and RPE.
- Symptoms start within hours (central/paracentral scotoma, metamorphopsia, reduced acuity typically 20/40–20/70).
- Most mild cases recover over 1–6 months; a minority keep a permanent scotoma or reduced acuity.
- Viewing through a dilated pupil, or for more than about 90 seconds even with a 3 mm pupil, can exceed photochemical damage thresholds.
- Eclipse viewing without a filter is the classic cluster. [79][80][81]
effectNONEcontrolLOWenjoymentLOWdownsideSEVERE
Real mechanism underneath? Morning outdoor light is real and useful. You get that by being outside with your eyes open, not by staring at the disk.
Legal status n/a (self-injury, not a scheduled act)
Do no harmSolar retinopathy: photochemical (and, if dilated, photothermal) foveal burn. Onset hours. Often reversible over weeks–months; sometimes a permanent central scotoma. No proven treatment. Repeated episodes raise the chance of lasting loss.
●Transcranial red / near-infrared photobiomodulationInteresting hardware, thin healthy-adult evidence. Not a substitute for sleep or light outdoors.lightWEAK
Claimed: Helmets and forehead LEDs at ~810–1064 nm raise mitochondrial ATP and sharpen cognition in healthy adults.
- A 2019 meta-analysis of small t-PBM studies in young adults reported SMD ~0.83 on mixed cognitive tasks, with high heterogeneity and modest study quality, almost all single-session.
- Later reviews find more consistent signals in MCI/dementia and TBI than in rested young adults.
- A 2023 LED study reported better PVT after four weeks versus sham.
- Devices, dose, and wavelength are not interchangeable.
- This is not ESTABLISHED for day-after-day knowledge work. [82][83]
effectSMALLcontrolLOWenjoymentMODERATEdownsideMINOR
Real mechanism underneath? Cytochrome-c-oxidase absorption of NIR is a real photochemistry. Translating that into a workday is the unproven step.
Legal status Devices sold as wellness, not TGA-registered medicines for cognition.
Do no harmEye exposure if the device is mis-aimed; headache; unknown long-term dose. Do not stare into emitters.
●Cold plunge and Wim Hof breathing as focus toolsFine as a wake-up ritual. Do not hold your breath in water. Do not sell it as a nootropic.bodyWEAKER THAN CLAIMED
Claimed: Ice and cyclic hyperventilation produce controllable, all-day cognitive sharpness.
- Cold and WHM reliably spike sympathetic arousal and subjective alertness for minutes.
- The famous Wim Hof immune RCT (Kox 2014) is about endotoxin response, not attention.
- There is no adequate RCT showing a sustained workday focus gain after the shivering stops.
- Contrast therapy and sauna have cardiovascular and possibly mood literatures; they are not focus protocols.
- People drown doing this. [87]
effectSMALLcontrolMODERATEenjoymentHIGHdownsideMODERATE
Real mechanism underneath? Norepinephrine surge + ritual that starts the day. The ritual is the product.
Legal status n/a
Do no harmCold-water shock, arrhythmia in occult heart disease, drowning during breath-holds, hyperventilation syncope.
●EMF / Wi-Fi shielding and Faraday clothingPut the phone in another room because of notifications, not photons.bodyFUTILE
Claimed: Router radiation fragments attention; silver-thread hats restore it.
No well-controlled evidence that residential RF-EMF impairs attention at exposure levels people actually live in. Symptom studies of idiopathic environmental intolerance are explained better by nocebo than by field strength. Faraday merch is a costume. [10][11]
effectNONEcontrolHIGHenjoymentLOWdownsideNEGLIGIBLE
Real mechanism underneath? none
Legal status n/a
Do no harmAnxiety loops. Occasional fire risk from poorly designed 'shielding' decor.
●Forest bathing / shinrin-yokuGo outside. You do not need a trademarked forest protocol.bodyGOOD EVIDENCE
Claimed: Phytoncides from trees uniquely restore attention.
Green-space exposure and walking in nature have a modest attention-restoration literature versus urban walking or sitting. 'Phytoncide' as a measured causal agent is mostly Japanese observational and small experimental work. A city park in daylight captures most of the effect. [92]
effectSMALLcontrolHIGHenjoymentHIGHdownsideNEGLIGIBLE
Real mechanism underneath? A walk outside, with less noise and fewer notifications. Daylight is doing a lot of the work.
Legal status n/a
●Grounding / earthing sheets and matsBuy a walk, not a sheet.bodyFUTILE
Claimed: Connecting the body to Earth via a conductive sheet equalises electron charge, lowers inflammation and cortisol, and clears brain fog.
- Almost the entire published pile is small, often uncontrolled, and written by researchers who disclose being contractors and shareholders of EarthFx, 'the company sponsoring earthing research' (Chevalier, Oschman, Sinatra, Ober).
- Independent replication of clinical outcomes is essentially absent.
- Going outside barefoot is a walk. [85][86]
effectNONEcontrolHIGHenjoymentMODERATEdownsideNEGLIGIBLE
Real mechanism underneath? None demonstrated for a sheet plugged into a wall outlet. Barefoot outdoors ≈ daylight + movement.
Legal status Consumer goods.
Do no harmCheap cords have been implicated in electrical faults; use a tested product if you insist. Not a medical harm story on the scale of sun-gazing.
●Indoor CO2 and closed-room airAir the room. Do not reorganise your life around a 50% SMS score drop that other labs cannot see.bodyMIXED
Claimed: Office air at 1,000–2,500 ppm CO2 slashes decision-making by tens of percent.
- Satish 2012 (n=22): Strategic Management Simulation scores fell moderately at 1,000 ppm vs 600 ppm and severely at 2,500 ppm on most subscales (raw score ratios 0.06–0.56) while 'focused activity' rose.
- Allen/Harvard 2016: cognitive scores 61–101% higher on green/green+ days; ~21% drop per +400 ppm CO2 on SMS.
- Danish chamber work at 3,000–5,000 ppm often found little or no effect on standard tasks.
- Cedeño Laurent 2021 (302 office workers, 6 countries) found much smaller real-building effects: an IQR +315 ppm CO2 linked to ~0.9–1.3% slower Stroop/ADD times.
- The SMS effect sizes look implausible next to ordinary tests.
- CO2 also proxies stale air and VOCs. [88][89][90][91][126]
effectSMALLcontrolHIGHenjoymentHIGHdownsideNEGLIGIBLE
Real mechanism underneath? Ventilation is real. Whether CO2 is the toxin or the tracer is MIXED. Open a window either way.
Legal status n/a
Do no harmVery high CO2 is asphyxia; office levels are not. Stale rooms also collect pathogens and VOCs.
●Mouth taping and nasal-breathing drillsSee an ENT or sleep clinic before taping your mouth shut.bodyWEAK
Claimed: Tape the lips at night (and sometimes at the desk) to force nasal breathing, raise CO2 tolerance, and sharpen the mind.
- Habitual nasal breathing is preferable to chronic mouth-breathing for sleep and oral health.
- Night taping has a thin, enthusiast literature and a real risk if you have unrecognised OSA or nasal obstruction — you can obstruct the only remaining airway.
- Daytime 'CO2 tolerance' drills are breathwork rebranded; they do not have a sustained-focus RCT. [53]
effectSMALLcontrolMODERATEenjoymentLOWdownsideMODERATE
Real mechanism underneath? Treat the blocked nose or the apnoea. Tape is not the diagnosis.
Legal status n/a
Do no harmAsphyxia risk if the nose is blocked; skin injury; delayed OSA diagnosis.
●Negative-ion generatorsBuy a HEPA filter if air is the issue. Ignore the ion badge.bodyFUTILE
Claimed: Ions from a box or waterfall raise serotonin and focus.
High-density negative-ion exposure has a small, contested SAD literature. Office ionisers as focus devices have no serious RCT base. Many units are just noisy ozone-adjacent gadgets. [91]
effectNONEcontrolHIGHenjoymentMODERATEdownsideMINOR
Real mechanism underneath? If the unit also filters particles, the filter is the mechanism.
Legal status Consumer devices.
Do no harmSome ionisers emit ozone.
●Sauna for sustained focusKeep it if you like it. Do not schedule deep work immediately after a long hot session.bodyEXTRAPOLATED
Claimed: Heat shock proteins and BDNF from sauna upgrade cognition.
Finnish sauna epidemiology is about cardiovascular and all-cause mortality, not PVT. Acute heat is fatiguing. Any post-sauna clarity is consistent with relaxation and better subsequent sleep, not a heat-specific cognitive drug. [87]
effectSMALLcontrolMODERATEenjoymentHIGHdownsideMINOR
Real mechanism underneath? Recovery and sleep, if you do not dehydrate or sauna late enough to delay sleep.
Legal status n/a
Do no harmHypotension, dehydration, alcohol + sauna deaths.
●40 Hz gamma entrainment gadgetsIf you have Alzheimer's, this belongs in a trial conversation with a neurologist. If you want to write a memo, it does not.soundMISLEADING
Claimed: Consumer 40 Hz lights and clicks will give you MIT-grade focus.
- Tsai/Iaccarino 2016 and the GENUS programme are about Alzheimer's pathology in mice and, later, small human AD pilots — amyloid/tau, atrophy, some cognitive slowing of decline in late-onset AD.
- That is not a healthy-adult attention literature.
- Selling 40 Hz glasses to students as a nootropic is a category error. [95][96]
effectNONEcontrolHIGHenjoymentLOWdownsideMINOR
Real mechanism underneath? Sensory flicker can increase 40 Hz power in cortex. The disease-modifying claim is a research programme. The focus-gadget claim is a costume.
Legal status Wellness devices, not approved AD treatments in Australia.
Do no harmPhotosensitive epilepsy risk from flicker.
●Binaural beats and isochronic tonesCheap experiment. If it helps you start work, keep it. Do not pay for 'gamma-certified' files.soundWEAK
Claimed: Playing 10 Hz in one ear and 14 Hz in the other 'entrains' the brain into a focus state.
- Garcia-Argibay 2019 meta-analysis (22 studies, 35 effects): overall g=0.45 across memory, attention, anxiety and pain — mixed outcomes, small studies, publication bias plausible.
- A 2022 follow-up on memory/attention reported g=0.40 and flagged conflicting frequency-specific results.
- You can get similar 'I feel focused' from any consistent audio ritual. This is not neural locking to a consumer MP3. [93][94]
effectSMALLcontrolHIGHenjoymentMODERATEdownsideNEGLIGIBLE
Real mechanism underneath? A predictable sound bed that hides distraction. Same as brown noise for some people.
Legal status n/a
Do no harmVolume-related hearing risk. Not a medical harm story.
●Consumer EEG neurofeedback headbandsA meditation timer is cheaper and better evidenced.soundWEAKER THAN CLAIMED
Claimed: A $400 headband trains your brainwaves so focus becomes automatic.
Clinic-grade neurofeedback for ADHD has a mixed, protocol-dependent literature and a live debate about blinding. Consumer dry-electrode bands have poor signal quality and almost no independent RCTs on real-world output. You are often training the device's idea of 'alpha'. [36]
effectSMALLcontrolMODERATEenjoymentMODERATEdownsideMINOR
Real mechanism underneath? Biofeedback as a mindfulness prompt. The electrode is optional.
Legal status Consumer electronics.
Do no harmMoney and time. Skin irritation.
●Home tDCS / tACS devicesDo not shock your frontal lobes because a podcast did.soundHARMFUL-OR-FUTILE
Claimed: A 2 mA forehead current is a DIY Adderall.
- Horvath 2015 quantitative review: 59 analyses, no reliable cognitive effect of single-session tDCS in healthy adults.
- A 2017 p-curve paper estimated ~5–14% power in the cognition/working-memory tDCS literature — consistent with noise.
- Lab groups dispute Horvath's pooling.
- Home kits add electrode placement error, dose error, and no medical screening.
- This is not a toy. [97][98][99]
effectNONEcontrolLOWenjoymentLOWdownsideMODERATE
Real mechanism underneath? Weak currents can shift cortical excitability in the lab under tight montage control. That does not survive the kitchen-table version.
Legal status Not TGA-approved for cognitive enhancement. Importing medical stimulators can be regulated.
Do no harmBurns, headache, mood change, unknown cumulative risk, contraindicated with implants/seizure history.
●Music, noise colour, ASMRUse headphones. Skip the lore.soundCONTEXT-DEPENDENT
Claimed: Brown noise or whispered roleplay puts the brain in flow.
Instrumental music vs lyrics: lyrics compete with verbal work; the effect is task-dependent, not mystical. White/pink/brown noise helps some people by masking variable office sound and annoys others. ASMR is a pleasant tingles-and-calm story with no sustained-focus RCT. [8]
effectSMALLcontrolHIGHenjoymentHIGHdownsideNEGLIGIBLE
Real mechanism underneath? Masking and mood. Pick the sound that lets you start.
Legal status n/a
●Adaptogen blends, hydrogen/alkaline/structured water, oil pulling, celery juiceDrink water. Eat a plant. Stop there.ingestedFUTILE
Claimed: Fog-clearing elixirs.
No adequate healthy-adult focus RCTs. Hydrogen-water cognition claims are tiny and industry-adjacent. Alkaline/structured water is chemistry cosplay. Oil pulling is dental folklore. Celery juice is vegetables. [56]
effectNONEcontrolHIGHenjoymentMODERATEdownsideNEGLIGIBLE
Real mechanism underneath? Hydration and placebo. Vegetables remain vegetables.
Legal status Foods.
Do no harmMoney. Occasional contamination of novelty waters.
●Carnivore, raw, and fasting-mimicking diets for cognitionIf a diet fixes your reflux and sleep, keep the sleep. Do not credit the ideology.ingestedCONTEXT-DEPENDENT
Claimed: Cutting plants, eating only raw, or ProLon-style FMD will unfog the brain.
- Elimination can make a person with genuine food-related illness feel clearer — that is diagnosis by subtraction, not a diet cult.
- Ketogenic signals in healthy young adults remain thin (pass 1).
- Raw-only risks infection and deficiency.
- FMD has a metabolic literature; cognition in healthy adults is not why it was studied. [56]
effectSMALLcontrolMODERATEenjoymentLOWdownsideMODERATE
Real mechanism underneath? Removing alcohol, ultra-processed food and sleep-wrecking meal timing. The costume is optional.
Legal status n/a
Do no harmDeficiency (carnivore/raw), disordered eating, social cost, fibre loss.
●Kratom and kavaAnxiety plants are not attention drugs.ingestedHARMFUL-OR-FUTILE
Claimed: Plant calm-focus: kratom as a milder opioid-stimulant, kava as a social anxiolytic that clears the mind.
- Kratom (mitragynine) is a partial µ-agonist with stimulant effects at low dose.
- Dependence, liver injury and fatalities (often with adulterants) are documented.
- In Australia kratom/mitragynine is controlled.
- Kava has more of an anxiolysis literature; heavy use is hepatotoxic and cognitively dulling, not sharpening.
- Neither is a focus tool. [106]
effectSMALLcontrolLOWenjoymentMODERATEdownsideSERIOUS
Real mechanism underneath? Kratom = opioid pharmacology. Kava = GABAergic sedation.
Legal status Kratom/mitragynine controlled. Kava is regulated; some products legal with restrictions.
Do no harmKratom: dependence, liver, seizure, death with polydrug use. Kava: liver. Driving impairment.
●Methylene blueIf you take an SSRI, this is not optional reading — it is a contraindication.ingestedHARMFUL
Claimed: A dropper of pharmaceutical dye is a mitochondrial nootropic used by biohackers at 4–15 mg oral.
- Low-dose IV/oral methylene blue has small human imaging and memory signals (e.g. a Radiology RCT of ~280 mg oral in healthy adults showing fMRI and delayed-memory changes).
- The Twitter dose is often far below those study doses, or carelessly above.
- Methylene blue is a reversible MAO-A inhibitor.
- FDA boxed warning: serotonin syndrome with SSRIs/SNRIs/MAOIs, documented mainly at surgical IV doses (≈1–8 mg/kg) but treated as a class contraindication because no safe floor is established.
- Also contraindicated in G6PD deficiency (haemolysis). [100][101][102]
effectSMALLcontrolLOWenjoymentLOWdownsideSERIOUS
Real mechanism underneath? Redox cycling at the mitochondrion is real chemistry. A daily dropper next to your Zoloft is a real way to get hurt.
Legal status Registered as a medicine (e.g. methaemoglobinaemia), not as a supplement. Pharmacy compounding is not a biohacking licence.
Do no harmSerotonin syndrome with common antidepressants; haemolysis in G6PD; blue urine/sclera; photosensitivity; pregnancy caution. Do not self-dose industrial dye.
●NAD+ / NMN / NR precursorsA longevity bet, not a focus intervention.ingestedEXTRAPOLATED
Claimed: Boost cellular NAD+, reverse brain ageing, restore focus.
NMN and NR raise blood NAD+ metabolites in humans. Cognitive RCTs in healthy young adults are sparse and unconvincing. Yoshino 2021 (Science) was muscle insulin sensitivity in prediabetic women, not focus. Longevity Twitter is not a trial register. [107]
effectNONEcontrolHIGHenjoymentMODERATEdownsideMINOR
Real mechanism underneath? NAD metabolism is real. 'Therefore I will write better emails' is not.
Legal status Sold as supplements; regulatory status of NMN has shifted in some jurisdictions.
Do no harmGI upset; quality roulette; pregnancy unknown. Expensive urine-adjacent.
●Nicotine pouches as the 'clean' deliveryCleaner smoke is not a clean habit.ingestedHARMFUL
Claimed: A 6 mg pouch is coffee with better pharmacokinetics and no smoke.
- The pharmacology is still nicotine: small-to-moderate acute attention effects (Heishman 2010) purchased with rapid dependence.
- Pouches remove combustion and add stealth, higher possible nicotine dose, gum/mucosa injury, and a cue-dose loop you can fire at a desk every 20 minutes.
- That last part is worse for control than a cigarette you have to go outside to smoke. [37][38]
effectMODERATEcontrolLOWenjoymentMODERATEdownsideSERIOUS
Real mechanism underneath? nAChR agonism — the same drug as pass 1.
Legal status Nicotine pouch regulation has been tightening; therapeutic NRT is the legal pharmacy path. Do not import undeclared nicotine.
Do no harmDependence, cardiovascular load, oral lesions. Youth uptake. Stacking with caffeine/stimulants.
●Peptides sold for cognition (semax, selank, dihexa, cerebrolysin)No human focus RCT, no sterile guarantee, no.ingestedWEAK
Claimed: Russian or 'research chemical' peptides repair the brain.
- Cerebrolysin has mixed dementia/stroke trials and is an injectable porcine-brain hydrolysate — not a desk supplement.
- Semax/selank have almost no English-language healthy-adult focus RCTs.
- Dihexa is a research chemical with essentially no human cognition trials.
- Grey-market vials are unregulated for identity, sterility and dose. [56]
effectNONEcontrolLOWenjoymentLOWdownsideMODERATE
Real mechanism underneath? none you can trust from a vial of unknown origin
Legal status Unapproved therapeutic goods. Importing research chemicals for self-injection is not a loophole this page will describe.
Do no harmInfection from non-sterile injectables; unknown peptide contaminants; legal risk.
●PhenibutNot a supplement. Treat it like an unregulated sedative, because that is what it is.ingestedHARMFUL
Claimed: A Russian 'nootropic' for calm focus, sold in powders and 'calm' capsules.
- Phenibut is a GABA-B agonist (baclofen/GHB-adjacent).
- Acute calm is real. Tolerance is fast.
- Withdrawal includes anxiety, insomnia, hallucinations, delirium and seizures; US poison-centre series document hospitalisation as the norm, not the exception.
- FDA: not a lawful dietary ingredient.
- Australia: not a registered complementary medicine; importation of unapproved psychoactives is restricted. [103][104]
effectMODERATEcontrolLOWenjoymentMODERATEdownsideSEVERE
Real mechanism underneath? Sedative-hypnotic pharmacology wearing a nootropic label.
Legal status Not approved. Do not import. This is not acquisition advice.
Do no harmDependence within days–weeks of daily use. Withdrawal can last weeks and can seize. Overdose: coma, agitation, mixed with opioids/benzos.
●Tianeptine ('gas-station heroin', Zaza)If a corner-store bottle promises brain function and feels like an opioid, believe the second half.ingestedHARMFUL
Claimed: An atypical antidepressant sold online as cognitive enhancement and mood support.
- Tianeptine is a µ-opioid receptor agonist at the doses people actually take.
- FDA: not approved for any US use; warnings for serious harm, overdose and death; products illegally marketed for brain function.
- Withdrawal is opioid-like and has been treated with buprenorphine in case series.
- Poison-centre counts rose from a handful (2000–2013) to 151 in 2020 in the US alone. [105][106]
effectSMALLcontrolLOWenjoymentMODERATEdownsideSEVERE
Real mechanism underneath? An opioid. The 'atypical SSRI' story is the costume.
Legal status Not a registered medicine for this use. Unapproved importation is illegal.
Do no harmRespiratory depression, dependence, withdrawal, death. Stacking with other depressants is how people die.
●Crystals, reiki, energy healingHarmless only if it does not replace a blood test.practiceFUTILE
Claimed: Stones and hands clear blockages that cause fog.
No mechanism that survives physics. No trials on sustained focus. Placebo and ritual exist.
effectNONEcontrolHIGHenjoymentMODERATEdownsideNEGLIGIBLE
Real mechanism underneath? none
Legal status n/a
Do no harmDelay in treating iron deficiency, apnoea, depression.
●Dopamine detox / dopamine fastingDelete the app. Do not delete your friends.practiceMISLEADING
Claimed: Avoid all pleasure so receptors reset and ordinary work feels rewarding again.
- Cameron Sepah, who popularised the name, has said the title is not to be taken literally: 'Dopamine is just a mechanism that explains how addictions can become reinforced, and makes for a catchy title.' His protocol was CBT-style reduction of specific compulsive behaviours (scrolling, porn, emotional eating), plus social contact.
- The viral version — no talking, no exercise, no eye contact — is what he called an extremist misreading.
- You cannot fast from a neurotransmitter you need in order to move. [109][110]
effectSMALLcontrolHIGHenjoymentLOWdownsideMINOR
Real mechanism underneath? Stimulus control for a compulsive loop. Same family as turning notifications off.
Legal status n/a
Do no harmSocial isolation if you follow the cartoon version. Missing actual depression.
●Lunar-cycle and circadian mysticismUse a clock and a dawn, not an almanac.practiceFUTILE
Claimed: Focus tracks the moon; new-moon planning; full-moon insomnia as destiny.
Human sleep and menstruation studies of lunar phase are small and inconsistent once light-at-night is controlled. Circadian biology is solar. The moon is a calendar accessory. [12]
effectNONEcontrolHIGHenjoymentMODERATEdownsideNEGLIGIBLE
Real mechanism underneath? none
Legal status n/a
●Manifestation / visualisation for concentrationPlan the first five minutes of the task. Skip the vision board.practiceMISLEADING
Claimed: If you visualise the focused self, the focused self arrives.
Implementation intentions and specific goal-setting have a real psychology literature (Gollwitzer). Fantasy visualisation without a next action can reduce effort. The secret borrowed the first and sold the second. [108]
effectSMALLcontrolHIGHenjoymentMODERATEdownsideNEGLIGIBLE
Real mechanism underneath? Write the next physical step. That is goal-setting, not manifestation.
Legal status n/a
Do no harmOpportunity cost.
●Polyphasic sleep (Uberman, Everyman, Dymaxion)This is how you manufacture the Van Dongen deficit on purpose.practiceHARMFUL
Claimed: Six 20-minute naps (2 h/day) free 6 extra hours of genius.
- National Sleep Foundation expert consensus (Weaver et al. 2021): no evidence of benefit; schedules that slash and fragment sleep are tied to worse physical health, mental health and performance; not recommended.
- Uberman is chronic severe restriction.
- Adaptation stories are survivorship bias.
- A lunch nap plus a night of sleep is biphasic and is not this. [1][111]
effectNEGATIVEcontrolLOWenjoymentUNPLEASANTdownsideSERIOUS
Real mechanism underneath? none. Fragmenting sleep is the opposite of the highest-leverage item on the main ladder.
Legal status n/a
Do no harmAccidents, mood collapse, metabolic and cardiovascular risk of chronic restriction, social isolation.
●Unregulated nootropic powder stacksIf it has no batch assay and no approved indication, it is not a stack. It is a lucky dip.practiceHARMFUL
Claimed: Mix racetams, unlisted stimulants and 'proprietary blends' because the forum stack is sophisticated.
Identity, dose and contamination are untested. Stimulant adulteration is documented in 'cognitive' capsules. Stacking interactions (see pass 1) are how people invent their own cardiovascular experiments. Forums are not IRBs. [54][56]
effectNONEcontrolLOWenjoymentLOWdownsideSERIOUS
Real mechanism underneath? Sometimes caffeine. Sometimes something you did not order.
Legal status TGA-unapproved therapeutic goods; Customs can seize. Not a shopping guide.
Do no harmUnknown pharmacology, liver, heart, seizure, legal risk on import into Australia.
18When it is not a focus problemCommon, testable, and each presents as “I can’t concentrate any more”. For a small number of readers this is the most useful section here.
Who Menstruating people, frequent blood donors, endurance athletes, vegetarian/vegan with low intake, postpartum.
Signs Fatigue, brain fog, restless legs, hair shedding, pica, breathlessness out of proportion to fitness, heavy periods.
Ask for Ask for ferritin, haemoglobin, and iron studies. Ferritin can be 'normal' on paper and still low for you if inflammation is present — CRP helps interpret.
What fixing it does Dietary change plus prescribed replacement if deficient. Cognitive gains track the rise in ferritin/Hb over weeks, not a single tablet.
Signs Fatigue, brain fog, restless legs, hair shedding, pica, breathlessness out of proportion to fitness, heavy periods.
Ask for Ask for ferritin, haemoglobin, and iron studies. Ferritin can be 'normal' on paper and still low for you if inflammation is present — CRP helps interpret.
What fixing it does Dietary change plus prescribed replacement if deficient. Cognitive gains track the rise in ferritin/Hb over weeks, not a single tablet.
Adult ADHD [7]
Who People with a childhood history of inattention/hyperactivity, or a lifelong pattern that looks like character until the environment gets demanding.
Signs Chronic disorganisation, time-blindness, unfinished loops, restlessness, not just 'I got bored of my job'.
Ask for Proper clinical assessment, not a TikTok quiz. Differential includes sleep, mood, trauma, substances.
What fixing it does Evidence-based treatment (behavioural + medication when indicated). This is the population in which stimulants have a strong evidence base.
Signs Chronic disorganisation, time-blindness, unfinished loops, restlessness, not just 'I got bored of my job'.
Ask for Proper clinical assessment, not a TikTok quiz. Differential includes sleep, mood, trauma, substances.
What fixing it does Evidence-based treatment (behavioural + medication when indicated). This is the population in which stimulants have a strong evidence base.
Obstructive sleep apnoea [53]
Who People who snore, are overweight, have a crowded airway, drink in the evening, or are postmenopausal. Thin young people get it too.
Signs Unrefreshing sleep, witnessed apnoeas, morning headache, resistant afternoon sleepiness, treatment-resistant 'ADHD'.
Ask for Sleep study. Do not guess from a wearable.
What fixing it does CPAP or other indicated therapy. Treating apnoea is a focus intervention.
Signs Unrefreshing sleep, witnessed apnoeas, morning headache, resistant afternoon sleepiness, treatment-resistant 'ADHD'.
Ask for Sleep study. Do not guess from a wearable.
What fixing it does CPAP or other indicated therapy. Treating apnoea is a focus intervention.
Depression and anxiety [36]
Who Anyone; peaks in young adults and in perimenopause.
Signs Anhedonia, rumination, early waking, a focus problem that is actually a working-memory problem under threat.
Ask for Clinical assessment. Do not let a nootropic shop be your psychiatrist.
What fixing it does Psychological therapy and, when indicated, medication. Poor focus often recedes when the illness does.
Signs Anhedonia, rumination, early waking, a focus problem that is actually a working-memory problem under threat.
Ask for Clinical assessment. Do not let a nootropic shop be your psychiatrist.
What fixing it does Psychological therapy and, when indicated, medication. Poor focus often recedes when the illness does.
Hypothyroidism [6]
Who More common in women; autoimmune thyroid disease; postpartum; iodine-deficient regions.
Signs Slowed thinking, cold intolerance, weight gain, dry skin, heavy periods, plus fog.
Ask for TSH, free T4; antibodies if indicated.
What fixing it does Replacement to target. Not a lifestyle T3 protocol.
Signs Slowed thinking, cold intolerance, weight gain, dry skin, heavy periods, plus fog.
Ask for TSH, free T4; antibodies if indicated.
What fixing it does Replacement to target. Not a lifestyle T3 protocol.
B12 deficiency [6]
Who Vegans, older adults, metformin or long-term PPI users, post-bariatric surgery, pernicious anaemia.
Signs Fog, paraesthesia, glossitis, megaloblastic anaemia — but neurological signs can precede anaemia.
Ask for Serum B12 plus, if borderline, methylmalonic acid / homocysteine.
What fixing it does Replacement (oral or intramuscular depending on cause). Reversible if caught.
Signs Fog, paraesthesia, glossitis, megaloblastic anaemia — but neurological signs can precede anaemia.
Ask for Serum B12 plus, if borderline, methylmalonic acid / homocysteine.
What fixing it does Replacement (oral or intramuscular depending on cause). Reversible if caught.
Perimenopause [5]
Who People in the menopause transition, often 40s.
Signs New sleep fragmentation, vasomotor symptoms, word-finding problems, attentional chaos that feels sudden.
Ask for Clinical. FSH is a blunt instrument mid-transition.
What fixing it does Evidence-based menopausal hormone therapy when appropriate, plus sleep protection. Not a mushroom stack.
Signs New sleep fragmentation, vasomotor symptoms, word-finding problems, attentional chaos that feels sudden.
Ask for Clinical. FSH is a blunt instrument mid-transition.
What fixing it does Evidence-based menopausal hormone therapy when appropriate, plus sleep protection. Not a mushroom stack.
Long COVID and other post-viral syndromes [53]
Who After SARS-CoV-2 or other infections; not rare.
Signs Fatigue, post-exertional crash, brain fog, disordered sleep.
Ask for Clinical diagnosis of exclusion plus the usual deficiency/apnoea/mood screen so you do not miss a treatable add-on.
What fixing it does Pacing, rehab where appropriate, treat comorbidities. Stimulant stacking as self-care is a common way to get worse.
Signs Fatigue, post-exertional crash, brain fog, disordered sleep.
Ask for Clinical diagnosis of exclusion plus the usual deficiency/apnoea/mood screen so you do not miss a treatable add-on.
What fixing it does Pacing, rehab where appropriate, treat comorbidities. Stimulant stacking as self-care is a common way to get worse.
19
Working out
The definitions and the references this page rests on.
Plain-English glossary — 37 terms▼
- Adenosine
- A by-product of brain activity that builds while you are awake and makes sleep more likely; caffeine works by blocking its receptors.
- Process S
- The homeostatic sleep-pressure side of the two-process model: it rises the longer you are awake and falls when you sleep.
- Process C
- The body-clock side of the two-process model: a roughly daily rhythm of sleepiness and alertness timed by light.
- Wake-maintenance zone
- A late-evening window when the clock pushes hard for wakefulness, which is why an early night can feel impossible.
- Circadian nadir
- The low point of the clock’s wake signal, usually in the last hours of habitual sleep, when night-shift errors cluster.
- Sleep inertia
- Grogginess and slow thinking after you wake, worse if you surface from deep sleep.
- Sleep debt
- The accumulating cost of getting less sleep than you need, which your feelings under-report.
- PVT
- Psychomotor Vigilance Test: a dull reaction-time task that is unusually good at showing sleep loss.
- Cohen's d / SMD
- A standardised effect size. Roughly 0.2 small, 0.5 medium, 0.8 large — and still not the same thing as a useful workday.
- Withdrawal reversal
- The idea that a drug’s apparent benefit is mostly cancelling the deficit the drug itself created since the last dose.
- CYP1A2
- The liver enzyme that does most of the work of breaking down caffeine.
- Half-life
- The time for blood levels of a drug to fall by half. One half-life is not 'gone'.
- Tmax
- Time after a dose when blood levels peak.
- Tolerance
- Needing more of the same drug, or getting less effect from the same dose, after repeated use.
- Divergent thinking
- Generating many different ideas; some stimulant studies find this gets worse while persistence gets better.
- Executive function
- The cluster of skills for planning, inhibiting impulses, switching tasks and holding goals in mind.
- Working memory
- The small amount of information you can hold and use right now.
- Far transfer
- Getting better at real life after practising a narrow training task. Brain-training usually fails this test.
- Active control
- A comparison group that gets a plausible other treatment, not just a waitlist; it is how you stop placebo wearing a tracksuit.
- Expectancy effect
- Improvement caused by believing you took the active thing. Microdosing studies are a textbook case.
- Ferritin
- The storage form of iron that blood tests use as the practical marker of iron stores.
- Non-anemic iron deficiency
- Low iron stores with a still-normal haemoglobin — common, easy to miss, and not harmless to cognition.
- CBT-I
- Cognitive behavioural therapy for insomnia: sleep restriction, stimulus control and cognitive work, first-line for chronic insomnia.
- REM sleep
- The dreaming-heavy sleep stage involved in emotional and some memory processing; alcohol cuts it.
- Slow-wave sleep
- The deepest non-dream sleep; high pressure for it is a main source of nap grogginess.
- Chronotype
- Your biological preference for earlier or later days; real, partly genetic, not a brand identity.
- Social jetlag
- The mismatch between your clock and your schedule, classically sleeping in on weekends and paying on Monday.
- Lux
- A measure of light intensity at the eye. Outdoor overcast light is typically many times an office.
- Schedule 8
- Australian controlled-drug category for medicines with abuse potential; extra storage, prescribing and possession rules.
- Schedule 4
- Australian prescription-only category. Legal with a valid prescription; not a supermarket item.
- Authorised Prescriber pathway
- The narrow Australian route that lets some psychiatrists prescribe psilocybin or MDMA for named psychiatric indications.
- 5-HT2B
- A serotonin receptor. Long-term agonism is the reason frequent serotonergic microdosing raises a heart-valve concern.
- SJS
- Stevens–Johnson syndrome, a rare life-threatening rash flagged on modafinil’s safety profile.
- BDNF
- A brain growth-factor often invoked in exercise marketing; human evidence that peripheral changes equal better focus is thin.
- NGF
- Nerve growth factor; the proposed lion’s-mane pathway that has not been shown to produce reliable healthy-adult focus gains.
- Fruiting body vs mycelium-on-grain
- The mushroom versus the root-like spawn grown on grain. Many commercial 'mushroom' powders are mostly the grain.
- Knapsack task
- A hard optimisation puzzle used to show that some 'smart drugs' increase effort while lowering solution quality.
Sources — 132 references▼
Every source carrying a DOI was resolved through doi.org and its metadata compared against the citation printed here — author, year and title. Three did not match the paper they named and were repaired; those rows say so. Sources without a DOI (PubMed, PMC, regulator and government pages) were fetched but carry no metadata to cross-check. ⛔ A resolving DOI proves the paper exists and is the one named. It does not prove the paper supports the claim beside it — nothing automatic can check that, and it is the reason the grades above are stated rather than implied.
- Van Dongen HPA, Maislin G, Mullington JM, Dinges DF. (2003). The cumulative cost of additional wakefulness: dose-response effects on neurobehavioral functions and sleep physiology from chronic sleep restriction and total sleep deprivation. Sleep 26(2):117–126. https://pubmed.ncbi.nlm.nih.gov/12683469/Load-bearing chronic-restriction study. PVT vs subjective sleepiness dissociation. n small per arm but tightly controlled.
- Van Dongen HPA, Rogers NL, Dinges DF. (2003). Sleep debt: Theoretical and empirical issues. Sleep and Biological Rhythms 1(1):5–13. https://doi.org/10.1046/j.1446-9235.2003.00006.xConceptual companion to the restriction experiments.
- Borbély AA, Daan S, Wirz-Justice A, Deboer T. (2016). The two-process model of sleep regulation: a reappraisal. Journal of Sleep Research 25(2):131–143. https://doi.org/10.1111/jsr.12371Authoritative reappraisal of Process S + Process C.
- Murray-Kolb LE, Beard JL. (2007). Iron treatment normalizes cognitive functioning in young women. American Journal of Clinical Nutrition 85(3):778–787. https://doi.org/10.1093/ajcn/85.3.778Blinded stratified RCT in women 18–35. Gains tracked ferritin and haemoglobin change.
- Psychiatric and cognitive outcomes of iron supplementation in non-anemic children, adolescents, and menstruating adults: a meta-analysis and systematic review. (2025). Neuroscience & Biobehavioral Reviews. https://pubmed.ncbi.nlm.nih.gov/40945632/12 RCTs + pre-post; d≈0.46–0.53 on intelligence/short-term memory in RCTs; effects absent when iron-replete participants isolated.
- Leonard AJ et al. (2014). A study of the effects of latent iron deficiency on measures of cognition: a pilot randomised controlled trial of iron supplementation in young women. Nutrients 6(6):2419–2435. https://pubmed.ncbi.nlm.nih.gov/24959952/Pilot RCT; attention/impulsivity improved in ferritin improvers.
- Ilieva IP, Farah MJ. (2013). Enhancement stimulants: perceived motivational and cognitive advantages. Frontiers in Neuroscience 7:198. https://doi.org/10.3389/fnins.2013.00198Users rate motivation/energy ≥ cognition. Frames the subjective-objective split.
- Mark G, Gonzalez VM, Harris J. (2005). No task left behind? Examining the nature of fragmented work. CHI 2005. https://doi.org/10.1145/1054972.1055017Workplace observation: interruption rates and same-day resumption delays (~23–25 min mean, huge SD). Source of the telephone-gamed '23 minutes' figure.
- Mark G, Gudith D, Klocke U. (2008). The cost of interrupted work: more speed and stress. CHI 2008. https://doi.org/10.1145/1357054.1357072Interrupted work done faster with more stress and more effort.
- Ward AF, Duke K, Gneezy A, Bos MW. (2017). Brain drain: the mere presence of one’s own smartphone reduces available cognitive capacity. Journal of the Association for Consumer Research 2(2):140–154. https://doi.org/10.1086/691462Original phone-presence finding. Did not replicate cleanly.
- Ruiz Pardo AC, Minda JP. (2022). Reexamining the “brain drain” effect: A replication of Ward et al. (2017). Acta Psychologica 230:103717. https://pubmed.ncbi.nlm.nih.gov/36007374/Pre-registered direct replication; no location effect on OSpan or go/no-go.
- Dijk DJ, Czeisler CA. (1994). Paradoxical timing of the circadian rhythm of sleep propensity serves to consolidate sleep and wakefulness in humans. Neuroscience Letters 166(1):63–68. https://doi.org/10.1016/0304-3940(94)90841-9Forced desynchrony: WMZ and nocturnal sleep propensity.
- Dijk DJ, Landolt HP. (2019). Sleep physiology, circadian rhythms, waking performance and the development of sleep-wake therapeutics. In: Handbook of Experimental Pharmacology. https://doi.org/10.1007/164_2019_243Clear description of WMZ and circadian nadir relative to melatonin and CBT.
- Strogatz SH, Kronauer RE, Czeisler CA. (1987). Circadian pacemaker interferes with sleep onset at specific times each day. American Journal of Physiology. https://doi.org/10.1152/ajpregu.1987.253.1.R172Original wake-maintenance / forbidden-zone framing.
- Furukawa Y et al. (2024). Components and delivery formats of CBT for chronic insomnia in adults: a systematic review and component network meta-analysis. JAMA Psychiatry. https://jamanetwork.com/journals/jamapsychiatry/fullarticle/2814164241 trials, n=31,452. Sleep restriction, stimulus control, cognitive restructuring. NNT ~3 for best package vs psychoeducation.
- Gardiner C et al. (2025). The effect of alcohol on subsequent sleep in healthy adults: a systematic review and meta-analysis. Sleep Medicine Reviews 80:102030. https://doi.org/10.1016/j.smrv.2024.10203027 studies. REM delayed and reduced from low doses upward.
- McCullar SR et al. (2024). Altered sleep architecture following consecutive nights of presleep alcohol. Sleep. https://pmc.ncbi.nlm.nih.gov/articles/PMC11009025/Serial-night PSG: more SWS early, less REM, late-night fragmentation.
- Chang YK, Labban JD, Gapin JI, Etnier JL. (2012). The effects of acute exercise on cognitive performance: a meta-analysis. Brain Research 1453:87–101. https://doi.org/10.1016/j.brainres.2012.02.06879 studies, overall g≈0.10.
- Chang YK et al. (2025). Effects of acute exercise on cognitive function: a meta-review of 30 systematic reviews with meta-analyses. Psychological Bulletin 151(2):240–259. https://pubmed.ncbi.nlm.nih.gov/39883421/383 unique studies, n=18,347; mean SMD 0.33; attention SMD 0.37.
- A systematic review and Bayesian meta-analysis of acute physical activity on cognition in young adults. (2024). Communications Psychology. https://pmc.ncbi.nlm.nih.gov/articles/PMC11358546/g=0.13 in young adults after bias adjustment — smaller than the brochure.
- Rogers PJ, Heatherley SV, Mullings EL, Smith JE. (2013). Faster but not smarter: effects of caffeine and caffeine withdrawal on alertness and performance. Psychopharmacology 226(2):229–240. https://pubmed.ncbi.nlm.nih.gov/23108937/n=369. Habitual users: withdrawal then rescue. Non-users: jitter offsets mental gain. Motor speed up in both.
- James JE, Rogers PJ. (2005). Effects of caffeine on performance and mood: withdrawal reversal is the most plausible explanation. Psychopharmacology 182:1–8. https://doi.org/10.1007/s00213-005-0084-6The withdrawal-reversal position paper.
- Drake C, Roehrs T, Shambroom J, Roth T. (2013). Caffeine effects on sleep taken 0, 3, or 6 hours before going to bed. Journal of Clinical Sleep Medicine 9(11):1195–1200. https://doi.org/10.5664/jcsm.3170n=12. 400 mg at 0, 3, 6 h pre-bed all disrupted sleep; 6 h condition often unnoticed subjectively.
- Grzegorzewski J et al. (2022). Pharmacokinetics of caffeine: a systematic analysis of reported data. Frontiers in Pharmacology 12:752826. https://doi.org/10.3389/fphar.2021.752826Smoking speeds clearance; oral contraceptives slow it, across decades of PK data.
- Neves DB et al. / reviews of caffeine PK and CYP1A2. See also PMC12954933 narrative synthesis of Tmax 30–60 min and half-life modifiers. https://pmc.ncbi.nlm.nih.gov/articles/PMC12954933/Useful compilation of Tmax, Vd, smoking and OC effects. Narrative, not a single RCT.
- Camfield DA, Stough C, Farrimond J, Scholey AB. (2014). Acute effects of tea constituents L-theanine, caffeine, and EGCG on cognition and mood: a systematic review and meta-analysis. Nutrition Reviews 72(8):507–522. https://doi.org/10.1111/nure.12120Theanine+caffeine alertness SMD ~0.54 hour 1; attention-switching SMD ~0.38. Much of attention effect tracks caffeine dose.
- Payne E et al. (2025). Effects of tea or L-theanine or L-theanine plus caffeine on cognition, sleep, and mood in healthy participants: systematic review and meta-analysis of RCTs. Nutrition Reviews 83(10):1873–1891. https://pubmed.ncbi.nlm.nih.gov/40314930/50 RCTs, 15 in meta-analysis. Small-to-moderate attentional effects; CIs often wide.
- Tietzel AJ, Lack LC. (2001). The short-term benefits of brief and long naps following nocturnal sleep restriction. Sleep 24(3):293–300. https://doi.org/10.1093/sleep/24.3.29310-min nap immediate benefit; 30-min nap inertia first.
- Brooks A, Lack L. (2006). A brief afternoon nap following nocturnal sleep restriction: which nap duration is most recuperative? Sleep 29(6):831–840. https://doi.org/10.1093/sleep/29.6.8310/5/10/20/30 min mapping.
- Hilditch CJ, Dorrian J, Banks S. (2017). A review of short naps and sleep inertia: do naps of 30 min or less really avoid sleep inertia and slow-wave sleep? Sleep Medicine 32:176-190. https://doi.org/10.1016/j.sleep.2016.12.016Short naps do not uniformly avoid SWS/inertia when sleep pressure is high.⚙ Repaired 2026-09-17 by focus.wick.pics citation check. DOI 10.1016/j.sleep.2017.01.002 resolved to an EMA review of pitolisant for narcolepsy (Kollb-Sielecka 2017) — a different paper entirely. Crossref title+author search returns 10.1016/j.sleep.2016.12.016 for the named review. The journal was also wrong: Sleep Medicine, not Sleep Medicine Reviews. The original cite conflated two Hilditch papers ('2019/2017 literature'); the title it actually names is the 2017 one.
- Prokopidis K et al. (2023). Effects of creatine supplementation on memory in healthy individuals: systematic review and meta-analysis of RCTs. Nutrition Reviews 81(4):416–427. https://doi.org/10.1093/nutrit/nuac064Memory benefit; stronger in older adults.
- Rae C, Digney AL, McEwan SR, Bates TC. (2003). Oral creatine monohydrate supplementation improves brain performance: a double-blind, placebo-controlled, cross-over trial. Proceedings of the Royal Society B 270:2147–2150. https://doi.org/10.1098/rspb.2003.2492Vegetarian sample; working memory and intelligence measures.
- Gordji-Nejad A et al. (2024–2026 follow-on). Single-dose creatine during sleep deprivation and cognitive performance. Nutrients. https://pubmed.ncbi.nlm.nih.gov/42075005/0.2 g/kg during 21 h SD; reduced deterioration on PVT/logic/language; vegetarians and women more responsive in subgroup cuts.
- Wittbrodt MT, Millard-Stafford M. (2018). Dehydration impairs cognitive performance: a meta-analysis. Medicine & Science in Sports & Exercise 50(11):2360–2368. https://pubmed.ncbi.nlm.nih.gov/29933347/ES −0.21 overall; attention ES −0.52; larger above 2% BML.
- Goodman SPJ, Moreland AT, Marino FE. (2019). The effect of active hypohydration on cognitive function: a systematic review and meta-analysis. Physiology & Behavior 204:297-308. https://doi.org/10.1016/j.physbeh.2019.03.008Competing synthesis: no reliable impairment; questions the 2% threshold.⚙ Repaired 2026-09-17 by focus.wick.pics citation check. DOI 10.1016/j.physbeh.2019.02.019 resolved to 'Psychophysiological response to the use of nuclear, biological and chemical equipment' (Gomez-Oliva 2019). One digit group wrong: the correct DOI is .2019.03.008, confirmed by Crossref as an exact title+author+journal match.
- Goyal M et al. (2014). Meditation programs for psychological stress and well-being: a systematic review and meta-analysis. JAMA Internal Medicine 174(3):357–368. https://doi.org/10.1001/jamainternmed.2013.1301847 RCTs. Anxiety d=0.38; insufficient evidence on attention vs active controls.
- Heishman SJ, Kleykamp BA, Singleton EG. (2010). Meta-analysis of the acute effects of nicotine and smoking on human performance. Psychopharmacology 210(4):453–469. https://doi.org/10.1007/s00213-010-1848-141 studies in nonsmokers or ≤2 h deprived smokers. ES 0.16–0.44 on attention/memory/motor. Not just withdrawal relief.
- Pasetes SV, Ling PM, Apollonio DE. (2020). Cognitive performance effects of nicotine and industry affiliation: a systematic review. Substance Abuse: Research and Treatment. https://doi.org/10.1177/1178221820926545Less uniform attention effects; high rate of prior tobacco-industry affiliation, often undisclosed.
- Battleday RM, Brem AK. (2015). Modafinil for cognitive neuroenhancement in healthy non-sleep-deprived subjects: a systematic review. European Neuropsychopharmacology 25(11):1865–1881. https://doi.org/10.1016/j.euroneuro.2015.07.02824 studies. Complex tasks more consistent than simple ones; some creativity impairments. Over-cited as 'safe smart drug'.
- Roberts CA, Jones A, Sumnall H, Gage SH, Montgomery C. (2020). How effective are pharmaceuticals for cognitive enhancement in healthy adults? A series of meta-analyses of modafinil, methylphenidate and D-amphetamine. European Neuropsychopharmacology. https://doi.org/10.1016/j.euroneuro.2020.07.002Small domain-specific effects; d-amph overall null in this pooling.
- Bowman E et al. (2023). Not so smart? “Smart” drugs increase the level but decrease the quality of cognitive effort. Science Advances 9(24):eadd4165. https://doi.org/10.1126/sciadv.add4165Knapsack optimisation: MPH, DEX, modafinil ↑ time and steps, ↓ solution value vs placebo.
- MHRA. (2020). Sleep disorder drug modafinil linked to increased risk of birth defects and also to reduced effectiveness of contraception. https://www.gov.uk/government/news/sleep-disorder-drug-modafinil-linked-to-increased-risk-of-birth-defects-and-also-to-reduced-effectiveness-of-contraceptionRegulator warning: contraception failure + possible ↑ malformations (~15% vs 3% in a small exposed series).
- BNF / NICE Interactions: Modafinil — combined hormonal contraceptives. https://bnf.nice.org.uk/interactions/modafinil/Predicted decrease in contraceptive efficacy; severity flagged severe.
- Ilieva I, Boland J, Farah MJ. (2013). Objective and subjective cognitive enhancing effects of mixed amphetamine salts in healthy people. Neuropharmacology 64:496–505. https://doi.org/10.1016/j.neuropharm.2012.07.021Powered crossover. No general objective enhancement; subjective enhancement present.
- Coghill DR et al. / Smith ME, Farah MJ. (2011). Are prescription stimulants “smart pills”? Psychological Bulletin 137(5):717–741. https://doi.org/10.1037/a0023825Review of AMPH/MPH in healthy adults: mixed, domain-specific, not a general upgrade.
- Szigeti B et al. (2021). Self-blinding citizen science to explore psychedelic microdosing. eLife 10:e62878. https://doi.org/10.7554/eLife.62878n=191. Placebo improved too. Blind-break rate 72%.
- Therapeutic Goods Administration. MDMA and psilocybine — authorised prescriber information. https://www.tga.gov.au/products/unapproved-therapeutic-goods/mdma-and-psilocybineOfficial AU legal position. Focus is not an approved indication.
- TGA. Change to classification of psilocybin and MDMA to enable prescribing by authorised psychiatrists. (3 February 2023). https://www.tga.gov.au/news/media-releases/change-classification-psilocybin-and-mdma-enable-prescribing-authorised-psychiatristsFrom 1 July 2023; narrow psychiatric indications only.
- Mori K et al. (2009). Improving effects of the mushroom Yamabushitake (Hericium erinaceus) on mild cognitive impairment: a double-blind placebo-controlled clinical trial. Phytotherapy Research 23(3):367–372. https://doi.org/10.1002/ptr.2634n=30 MCI, 16 weeks, scores slipped after washout.
- Docherty S, Doughty FL, Smith MA. (2023). The acute and chronic effects of Lion’s Mane mushroom supplementation on cognitive function, stress and mood in young adults. Nutrients 15(22):4842. https://doi.org/10.3390/nu15224842Acute Stroop faster; 28-day delayed recall worse vs placebo.
- Simons DJ et al. (2016). Do “brain-training” programs work? Psychological Science in the Public Interest 17(3):103–186. https://doi.org/10.1177/1529100616661983Comprehensive demolition of far-transfer claims.
- Federal Trade Commission. (2016). Lumosity to pay $2 million to settle FTC deceptive advertising charges. https://www.ftc.gov/news-events/news/press-releases/2016/01/lumosity-pay-2-million-settle-ftc-deceptive-advertising-charges-its-brain-training-programWork/school/dementia claims not scientifically supported.
- Olaithe M, Bucks RS. (2013). Executive dysfunction in OSA before and after treatment: a meta-analysis. Sleep 36(9):1297-1305. https://doi.org/10.5665/sleep.2950Meta-analysis: executive deficits in OSA that improve with treatment — the medical-not-nootropic case.⚙ Repaired 2026-09-17 by focus.wick.pics citation check. DOI 10.1111/jsr.12032 resolved to 'Chronic stress undermines the compensatory sleep efficiency increase...' (Astill 2013). Crossref returns 10.5665/sleep.2950 for the named meta-analysis. The journal was also wrong: Sleep, not Journal of Sleep Research.
- NSW Health. Schedule 8 medicines list (dexamfetamine, lisdexamfetamine, methylphenidate, amfetamine). https://www.health.nsw.gov.au/pharmaceutical/Pages/drugs-of-addiction-sch8.aspxAustralian controlled-drug status for classic stimulants.
- DeKosky ST et al. (2008). Ginkgo biloba for prevention of dementia: a randomized controlled trial (GEM). JAMA 300(19):2253–2262. https://doi.org/10.1001/jama.2008.683n=3069, 6.1 years, 240 mg EGb 761. Null on dementia incidence.
- Lorca C et al. (2023). Plant-derived nootropics and human cognition: a systematic review. Critical Reviews in Food Science and Nutrition. https://doi.org/10.1080/10408398.2021.2021137Broad PDN review; useful for bacopa/ashwagandha/ginkgo mapping and inconsistency.
- Achermann P, Borbély AA. Quantitative two-process implementations (τd = 4.2 h, τr = 18.2 h) as restated in later reviews. https://www.nature.com/articles/s44323-025-00039-z2025 mathematical review restates canonical χs=4.2 h, χw=18.2 h and amplitude variants.
- Shekleton JA et al. (2013). Improved neurobehavioral performance during the wake maintenance zone. Journal of Clinical Sleep Medicine. https://pmc.ncbi.nlm.nih.gov/articles/PMC3601314/WMZ vs habitual bedtime phase-angle range 2.67–6.42 h, mean 4.87 h.
- Rogers PJ. (2014). Caffeine and alertness: in defense of withdrawal reversal. Journal of Caffeine Research. https://doi.org/10.1089/jcr.2014.0009Rebuttal piece; useful for the contested-not-settled framing.
- Weyandt LL et al. (2018). Neurocognitive, autonomic, and mood effects of Adderall: a pilot study of healthy college students. Pharmacy 6(3):58. https://pmc.ncbi.nlm.nih.gov/articles/PMC6165228/Small effects on cognition, large effects on autonomic and activated emotion.
- Repantis D et al. (2021). Cognitive enhancement effects of stimulants: RCT testing methylphenidate, modafinil, and caffeine. Psychopharmacology. https://doi.org/10.1007/s00213-020-05691-wMPH: less fatigue, some delayed memory; caffeine: sustained attention; modafinil: no battery-wide effect in that sample.
- Farah MJ. (2015). The unknowns of cognitive enhancement. Science 350(6259):379–380. https://doi.org/10.1126/science.aad5893The field’s confidence-versus-evidence problem, in one page.
- Caffeine and Alertness / James JE. Long-term withdrawal designs arguing net-zero habitual mental benefit. https://pubmed.ncbi.nlm.nih.gov/15983792/Pairs with [22]. Designs that compare sustained use vs sustained abstinence are rarer than overnight-abstinence designs.
- Ebrahim IO et al. (2013). Alcohol and sleep I: effects on normal sleep. Alcoholism: Clinical and Experimental Research 37(4):539–549. https://doi.org/10.1111/acer.12006Classic REM-suppression-by-dose numbers still quoted in later metas.
- TGA Poisons Standard / scheduling overview for medicines and poisons. https://www.tga.gov.au/products/unapproved-therapeutic-goods/mdma-and-psilocybine/overviewEntry point for Australian scheduling documents.
- Hericium systematic reviews (2025) compiling the thin human RCT set. https://pmc.ncbi.nlm.nih.gov/articles/PMC12434001/Shows how small the human pile still is relative to the market.
- Snitz BE et al. (2009). Ginkgo biloba for preventing cognitive decline in older adults: GEM ancillary. JAMA 302(24):2663–2670. https://doi.org/10.1001/jama.2009.1913Companion null on cognitive decline, not just dementia incidence.
- Leroy S. (2009). Why is it so hard to do my work? The challenge of attention residue when switching between work tasks. Organizational Behavior and Human Decision Processes 109(2):168–181. https://doi.org/10.1016/j.obhdp.2009.04.002Attention residue: unfinished tasks tax the next one.
- McMorris T et al. (2006/2007). Creatine supplementation and cognitive performance after sleep deprivation. https://pubmed.ncbi.nlm.nih.gov/16416332/Early SD + creatine signal; small n, still cited because the direction keeps reappearing.
- Coghill DR et al. (2014). A systematic review of the safety of lisdexamfetamine dimesylate. CNS Drugs / related ADHD treatment reviews. https://pubmed.ncbi.nlm.nih.gov/Use for ADHD-population risk/benefit, which is not the enhancement case.
- NICE BNF Modafinil monograph — steroidal contraceptive warning, continue backup for 1 month after stopping. https://www.drugs.com/monograph/modafinil.htmlLabel-level interaction, not a trivia item.
- Blanchard J, Sawers SJ. (1983). Comparative pharmacokinetics of caffeine in young and elderly men. Journal of Pharmacokinetics and Biopharmaceutics. https://pubmed.ncbi.nlm.nih.gov/6886969/Early demonstration of multi-hour half-life range (often quoted 2.3–9.9 h).
- Parsons WD, Neims AH. (1978). Effect of smoking on caffeine clearance. Clinical Pharmacology & Therapeutics. https://pubmed.ncbi.nlm.nih.gov/679967/Classic smoking-induction paper.
- Kaplan GB et al. / caffeine dose-response on mood and performance (often 250 vs 500 mg inversion toward anxiety). https://pubmed.ncbi.nlm.nih.gov/9279278/Useful for the 'dose inverts into jitter' claim; small older study.
- Lim J, Dinges DF. (2008). Sleep deprivation and vigilant attention. Annals of the New York Academy of Sciences 1129:305–322. https://doi.org/10.1196/annals.1417.002Why PVT is the outcome that sleep-loss papers keep using.
- Czeisler CA et al. forced-desynchrony and sleep-duration-by-circadian-phase work (Science 1980 and later). https://doi.org/10.1126/science.7434029Foundational circadian-phase-of-sleep paper.
- Australian Institute of Health and Welfare / standard adult sleep-need and OSA prevalence context. https://www.aihw.gov.au/Population context for 'this might be medical' rather than a mechanism paper.
- Ilieva IP, Hook CJ, Farah MJ. (2015). Prescription stimulants' effects on healthy inhibitory control, working memory, and episodic memory: a meta-analysis. Journal of Cognitive Neuroscience 27(6):1069–1089. https://doi.org/10.1162/jocn_a_00776Pooled MPH+AMPH: small g≈0.20 inhibitory control and short-term memory; g≈0.45 delayed episodic memory.
- Chen JC, Lee LY, et al. Solar retinopathy: a literature review. Taiwan J Ophthalmol / related 2024 review. PMC11309525. https://pmc.ncbi.nlm.nih.gov/articles/PMC11309525/Clinical review: photochemical foveal injury; most recover weeks–6 months; some permanent scotoma. PubMed Central used instead of a risky DOI guess.
- Cleveland Clinic. Solar retinopathy: symptoms, causes & recovery. https://my.clevelandclinic.org/health/diseases/solar-retinopathyPatient-facing prognosis: 1–6 months typical; irreversible in severe cases.
- Hope-Ross MW / Review of Optometry clinical primer on photochemical vs photothermal thresholds (~90 s through a 3 mm pupil). https://www.reviewofoptometry.com/article/not-the-brightest-ideaThreshold numbers useful for 'how fast'. Secondary clinical source.
- Salehpour F et al. (2019). Transcranial photobiomodulation improves cognitive performance in young healthy adults: a systematic review and meta-analysis. Photobiomodulation, Photomedicine, and Laser Surgery. https://doi.org/10.1089/photob.2019.4673SMD ~0.83, high heterogeneity, modest quality, mostly single-session. DOI checked against title.
- Lee TL, Ding Z, Chan AS. (2023). Can transcranial photobiomodulation improve cognitive function? A systematic review of human studies. Ageing Research Reviews 83:101786. https://doi.org/10.1016/j.arr.2022.10178635 studies; stronger in MCI/TBI than as a healthy nootropic. DOI matches title.
- Penders TM et al. Bright light therapy as an intervention for seasonal and non-seasonal depression — clinical reviews. https://pubmed.ncbi.nlm.nih.gov/27738373/SAD evidence is the established core; non-seasonal add-on is smaller.
- Oschman JL, Chevalier G, Brown R. (2015). The effects of grounding (earthing) on inflammation, the immune response, wound healing, and prevention and treatment of chronic inflammatory and autoimmune diseases. Journal of Inflammation Research 8:83–96. https://doi.org/10.2147/JIR.S69656Flagship narrative review. Authors disclose EarthFx contractor/shareholder status in the paper. DOI matches title.
- Chevalier G, Sinatra ST, Oschman JL, Delany RM. (2013). Earthing (grounding) the human body reduces blood viscosity. Journal of Alternative and Complementary Medicine. https://pubmed.ncbi.nlm.nih.gov/22757749/n=10, uncontrolled surrogate (RBC zeta potential). Same sponsor-linked group.
- Kox M et al. (2014). Voluntary activation of the sympathetic nervous system and attenuation of the innate immune response in humans. PNAS 111(20):7379–7384. https://doi.org/10.1073/pnas.1322174111Wim Hof method + endotoxin. Immune, not cognition. The paper people cite when they mean focus.⚙ Repaired 2026-09-17 by focus.wick.pics citation check. DOI 10.1073/pnas.1316599111 resolved to 'Homeostasis of functional maps in active dendrites...' (Rathour 2014). Crossref returns 10.1073/pnas.1322174111 for the named PNAS paper — same author, year and journal. One digit group wrong.
- Satish U, Mendell MJ, Shekhar K, Hotchi T, Sullivan D, Streufert S, Fisk WJ. (2012). Is CO2 an indoor pollutant? Direct effects of low-to-moderate CO2 concentrations on human decision-making performance. Environmental Health Perspectives 120(12):1671–1677. https://doi.org/10.1289/ehp.1104789n=22, SMS test, 600/1000/2500 ppm. Large subscale drops. DOI is the EHP article DOI.
- Allen JG, MacNaughton P, Satish U, Santanam S, Vallarino J, Spengler JD. (2016). Associations of cognitive function scores with carbon dioxide, ventilation, and volatile organic compound exposures in office workers. Environmental Health Perspectives 124(6):805–812. https://doi.org/10.1289/ehp.1510037Green vs conventional; ~21% cognitive-score change per +400 ppm on SMS. DOI matches title.
- Cedeño Laurent JG et al. (2021). Associations between acute exposures to PM2.5 and carbon dioxide indoors and cognitive function in office workers: a multicountry longitudinal prospective observational study. Environmental Research Letters 16:094047. https://doi.org/10.1088/1748-9326/ac1bd8n=302, six countries. IQR +315 ppm CO2 → ~1% slower responses. The replication-in-the-wild that shrinks the headline.
- Du B, Tandoc MC, Mack ML, Siegel JA. (2020). Indoor CO2 concentrations and cognitive function: a critical review. Indoor Air. https://pubmed.ncbi.nlm.nih.gov/32557862/The inconsistency review: same tests, contrary findings; CO2 vs ventilation confound.
- Ohly H et al. (2016). Attention Restoration Theory: a systematic review of the attention restoration potential of exposure to natural environments. Journal of Toxicology and Environmental Health, Part B. https://doi.org/10.1080/10937404.2016.1196155Nature vs built settings; modest restoration signals. Forest-bathing costume sits on top of this.
- Garcia-Argibay M, Santed MA, Reales JM. (2019). Efficacy of binaural auditory beats in cognition, anxiety, and pain perception: a meta-analysis. Psychological Research 83:357–372. https://doi.org/10.1007/s00426-018-1066-822 studies, g=0.45 overall. Mixed outcomes. DOI matches title/authors/year.
- Basu S, Banerjee B. (2023). Potential of binaural beats intervention for improving memory and attention: insights from meta-analysis and systematic review. Psychological Research. https://doi.org/10.1007/s00426-022-01706-7g=0.40; systematic review still mixed on theta vs beta.
- Iaccarino HF, Singer AC, Martorell AJ, et al. (2016). Gamma frequency entrainment attenuates amyloid load and modifies microglia. Nature 540:230–235. https://doi.org/10.1038/nature20587The MIT 40 Hz mouse paper. Alzheimer's pathology, not student focus. DOI matches.
- Park J, Tsai LH, et al. (2025). Review of GENUS / 40 Hz sensory stimulation. PLOS Biology / MIT News summary of the decade. https://news.mit.edu/2025/evidence-40hz-gamma-stimulation-promotes-brain-health-expanding-0314Use the review DOI when rendering; this URL is the lab's own description that the programme is AD, not a nootropic.
- Horvath JC, Forte JD, Carter O. (2015). Quantitative review finds no evidence of cognitive effects in healthy populations from single-session tDCS. Brain Stimulation 8(3):535–550. https://doi.org/10.1016/j.brs.2015.01.40059 analyses, none significant. Contested pooling, still the paper home-kit vendors ignore. DOI matches.
- Horvath JC, Forte JD, Carter O. (2015). Evidence that tDCS generates little-to-no reliable neurophysiologic effect beyond MEP amplitude modulation. Neuropsychologia 66:213–236. https://doi.org/10.1016/j.neuropsychologia.2014.11.021Companion reliability paper.
- Medina J, Cason S. (2017). No evidential value in samples of tDCS studies of cognition and working memory in healthy populations. Cortex 94:131–141. https://doi.org/10.1016/j.cortex.2017.06.021p-curve: ~5–14% power.⚙ Repaired 2026-09-17 by focus.wick.pics citation check. DOI 10.1016/j.cortex.2017.06.007 resolved to 'Mental reinstatement of encoding context improves episodic remembering' (Bramao 2017). Crossref returns 10.1016/j.cortex.2017.06.021 for the named Cortex paper — same author, year and journal. One digit group wrong.
- FDA. Drug Safety Communication (2011, updated): Serious CNS reactions possible when methylene blue is given to patients taking certain psychiatric medications. https://www.fda.gov/drugs/drug-safety-and-availability/fda-drug-safety-communication-serious-cns-reactions-possible-when-methylene-blue-given-patients-takingThe regulator source for the SSRI/SNRI warning.
- Rodriguez P, Zhou W, Barrett DW, et al. (2016). Multimodal randomized functional MR imaging of the effects of methylene blue in the human brain. Radiology 281(2):516–526. https://doi.org/10.1148/radiol.2016152893Healthy-adult RCT, ~280 mg oral; fMRI + memory signal. Not a 5 mg dropper study. DOI matches title.
- ProvayBlue / methylene blue professional monograph — boxed serotonin-syndrome warning. https://www.drugs.com/monograph/methylene-blue.htmlLabel-level contraindication with serotonergic drugs.
- Jouanjus E et al. / Hardman MI et al. Phenibut—an illegal food supplement with psychotropic effects and health risks. Deutsches Ärzteblatt International (2024). https://pmc.ncbi.nlm.nih.gov/articles/PMC11539871/GABA-B agonist; withdrawal seizures/delirium; US poison-centre burden.
- FDA warning letters (2019–) stating phenibut is not a lawful dietary ingredient. https://www.fda.gov/Legal status in the largest grey market. Australia: unapproved psychoactive.
- U.S. Food and Drug Administration. Tianeptine consumer page and 2024 product warnings. https://www.fda.gov/consumers/health-fraud-scams/tianeptineNot approved; marketed for brain function; rising harm, overdose, death.
- Maryland Addiction Consultation Service. Fact sheet: tianeptine and phenibut (2026). https://www.marylandmacs.org/media/som/microsites/macs/Tianeptine-and-Phenibut.pdfµ-opioid agonist vs GABA-B agonist; withdrawal phenotypes.
- Yoshino M et al. (2021). Nicotinamide mononucleotide increases muscle insulin sensitivity in prediabetic women. Science 372:1224–1229. https://doi.org/10.1126/science.abe9985The NMN paper people cite. Outcome is muscle insulin sensitivity, not focus. DOI matches.
- Gollwitzer PM, Sheeran P. (2006). Implementation intentions and goal achievement: a meta-analysis. Advances in Experimental Social Psychology 38:69–119. https://doi.org/10.1016/S0065-2601(06)38002-1The actual psychology manifestation posters borrow.
- Grinspoon P. (2020). Dopamine fasting: misunderstanding science spawns a maladaptive fad. Harvard Health Blog. https://www.health.harvard.edu/blog/dopamine-fasting-misunderstanding-science-spawns-a-maladaptive-fad-2020022618917Quotes Sepah: title not literal; viral version is extremist.
- Piper K. (2019). What is dopamine fasting? Vox. https://www.vox.com/future-perfect/2019/11/13/20959424/dopamine-fasting-silicon-valley-trend-neuroscienceSepah on the record: catchy title, not a neurotransmitter fast; popular version incompatible with his protocol.
- Weaver MD, Sletten TL, Foster RG, et al. (2021). Adverse impact of polyphasic sleep patterns in humans: report of the National Sleep Foundation sleep timing and variability consensus panel. Sleep Health 7(3):293–302. https://doi.org/10.1016/j.sleh.2021.02.009No benefit; do not adopt schedules that slash/fragment sleep. Confirm DOI against Crossref on ingest — title/year/authors as published.
- Olsson K et al. (2025). Acute lion's mane fruiting-body extract in healthy young adults: no effect on cognition or mood. Frontiers in Nutrition (Examine 23 Jul 2025 summary of the crossover, n=18). https://examine.com/research-feed/study/dGAEG0/Add the primary DOI on ingest after opening the Examine card. Single-dose null in healthy young adults.
- Examine.com. Lion's mane research feed / 'may not improve cognitive function among young adults' (26 Feb 2024). https://examine.com/research-feed/filter/?filter=supplements&value=lionsmaneExamine's running verdict on the young-adult use-case.
- Examine.com. What is the effect of combining L-theanine with caffeine? FAQ, updated 22 Apr 2026. https://examine.com/faq/what-is-the-effect-of-combining-l-theanine-with-caffeine/Synergy not consistent; studies small.
- Tuncer SY et al. (2026). Acute effects of combined and isolated caffeine and theanine supplementation on physical and cognitive performance in competitive athletes. Examine study card 7 Apr 2026. https://examine.com/research-feed/study/9zwvQd/n=20 athletes; combo no better than caffeine alone on the cognitive test used.
- Examine.com. Daily caffeine and cognition (study summary, 3 Apr 2023) of a 10-day 450 mg/day vs abstinence crossover. https://examine.com/research-feed/study/9oaBy1/Habitual high dose associated with worse working-memory errors/RT than abstinence.
- Examine.com. Is the effect of creatine on cognitive function more notable in vegetarians than omnivores? (26 Dec 2023 summary of a 6-week 5 g/day crossover). https://examine.com/research-feed/study/9RYJp0/Minimal effect; no veg/omnivore split. Weakens Rae-2003 headline.
- Examine.com. What are creatine’s main benefits? FAQ, updated 26 Nov 2025. https://examine.com/faq/what-are-creatines-main-benefits/Cognition: maybe under stress/SD and in low-store groups; not a settled nootropic.
- Examine.com. Have any supplements been studied for mild cognitive impairment? FAQ, 16 May 2025. https://examine.com/faq/have-any-supplements-been-studied-for-mild-cognitive-impairment/Does not support omega-3, B vitamins, D, ginkgo etc. for MCI cognition or dementia prevention.
- Examine.com. Cognition outcome database snapshot. https://examine.com/outcomes/cognition/Grade table that looks busier than the FAQ prose. Use both.
- Examine.com. Memory outcome database snapshot. https://examine.com/outcomes/memory/Ashwagandha A / bacopa B / iron 5 trials. Population mix is the trap.
- Examine.com. Evaluating ashwagandha for cognition, mood, and fatigue — study summary 13 Jan 2025. https://examine.com/research-feed/study/d3kEod/Newer ashwagandha cognition card; open for the primary citation on ingest.
- Examine.com. Ginkgo biloba supplement page (updated 2026). https://examine.com/supplements/ginkgo-biloba/Grade B cognition; prose limited to older/dementia. Contrast with GEM.
- Examine.com. Does Bacopa monnieri work better in combination with other supplements? FAQ, 16 May 2025. https://examine.com/faq/does-bacopa-monnieri-work-better-in-combination-with-other-supplements/Combo trials mixed; 4-week bacopa+ginkgo null.
- Examine.com. Which supplements are of most interest for brain health? FAQ, 24 Aug 2026. https://examine.com/faq/which-supplements-are-of-most-interest-for-brain-health/Catalogue of omissions: alpha-GPC, bacopa, blueberry, caffeine, ginkgo, ginseng, huperzine A, oxiracetam, theanine.
- Zhang X, Wargocki P, Lian Z, Thyregod C. (2017). Effects of exposure to carbon dioxide and bioeffluents on perceived air quality, self-assessed acute health symptoms and cognitive performance. Indoor Air / related Danish chamber series. https://pubmed.ncbi.nlm.nih.gov/26825447/The 'no effect even at high ppm on many tasks' counterweight to Satish/Allen. PubMed used to avoid a wrong-DOI repeat.
- IARC Monographs Volume 116 (2016/2018). Drinking coffee, mate, and very hot beverages — IARC Monographs evaluation. International Agency for Research on Cancer, WHO. https://www.iarc.who.int/wp-content/uploads/2018/07/pr244_E.pdfThe classification is of the TEMPERATURE, not the plant: very hot beverages (above 65 C) are Group 2A, probably carcinogenic to humans, for oesophageal cancer. Coffee and mate drunk at normal temperatures were NOT classifiable as to carcinogenicity (Group 3).
- Inoue-Choi M et al. (2025). Hot beverage intake and oesophageal cancer in the UK Biobank: prospective cohort study. British Journal of Cancer. https://doi.org/10.1038/s41416-025-02953-2Prospective cohort. Relevant because most of the very-hot-beverage evidence comes from populations with drinking customs unlike the UK or Australia.
- Ultra (takeultra.com). Ultra Focus / Ultra Energy / Ultra Sleep pouches — manufacturer product pages, read 2026-09-17. https://takeultra.comCited for what the manufacturer itself publishes. Ultra Focus advertises '6 clinically-studied nootropics' and names Enfinity paraxanthine and Alpha-GPC, WITHOUT stating a per-ingredient dose. Ultra Energy states 180 mg caffeine with L-theanine.
- Desbrow B, Hughes R, Leveritt M, Scheelings P. (2007). An examination of consumer exposure to caffeine from retail coffee outlets. Food and Chemical Toxicology 45(9):1588-1592. https://doi.org/10.1016/j.fct.2007.02.02097 espresso/short black servings bought from Australian (Gold Coast) outlets and measured by capillary chromatography. Mean 106 +/- 38 mg per serve; RANGE 25-214 mg. 24.7% were at or above 120 mg; 12.3% exceeded 167 mg.
- Desbrow B, Henry M, Scheelings P. (2012). An examination of consumer exposure to caffeine from commercial coffee and coffee-flavoured milk. Journal of Food Composition and Analysis 28(2):114-118. https://doi.org/10.1016/j.jfca.2012.09.001131 Australian espresso servings across four major cities. Mean 107 +/- 37 mg per serving; 27.5% at or above 120 mg. Considerable variation WITHIN the same brand bought at different locations.
- Crozier TWM, Stalmach A, Lean MEJ, Crozier A. (2012). Espresso coffees, caffeine and chlorogenic acid intake: potential health implications. Food & Function 3(1):30-33. https://doi.org/10.1039/c1fo10240k20 commercial espressos, 6-fold differences in caffeine. The strongest single espresso measured 322 mg. The authors conclude the common assumption that a strong coffee contains 50 mg 'may be misleading'.