The Sunlight Experiment

Supplement Monograph

L-Theanine

NootropicAmino Acid

A calming amino acid from tea that sharpens attention and takes the edge off caffeine without sedation.

Work in progress Updated July 2026

Where Does It Come From? (3)

Bay boleteGuayusa Tea Camellia sinensis

Pharmacology & Research

L-theanine (N-ethyl-L-glutamine) is a non-proteinogenic amino acid found almost exclusively in the tea plant (Camellia sinensis), structurally related to glutamate. It crosses the blood–brain barrier and is one of the most popular relaxation and “calm focus” nootropics — but unlike a vitamin or mineral, there is no deficiency to correct, so every reported effect is an extra-on-top pharmacological action rather than repletion. The strongest and most consistent evidence is for acute attention, especially when it is paired with caffeine; the relaxation, sleep and mood claims are real but smaller and less consistent than the marketing implies. A recurring caveat across the literature is that many trials used branded formulations (Suntheanine, AlphaWave) or theanine-plus-caffeine mixtures rather than pure L-theanine, and several carry industry funding — so effect sizes should be read as modest and provisional.

What the evidence supports
  • Best-supported: acute improvement in attention and reaction time, particularly the L-theanine + caffeine combination on demanding attention-switching tasks 1,6,7,10Reference 1Gerolymos C et al. · 2026Meta-analysisCognitive and affective effects of L-Theanine: a systematic review and meta-analysis of 31 randomized trials — meta-analysisView study →Reference 6Owen GN et al. · 2008RCTThe combined effects of L-theanine and caffeine on cognitive performance and mood — RCTView study →Reference 7Giesbrecht T et al. · 2010RCTThe combination of L-theanine and caffeine improves cognitive performance and increases subjective alertness — RCTView study →Reference 10Payne ER et al. · 2025Meta-analysisEffects of Tea or its Bioactive Compounds L-Theanine or L-Theanine plus Caffeine on Cognition, Sleep, and Mood in Healthy Participants: Systematic Review and Meta-AnalysisView study →. A 2026 meta-analysis of 31 RCTs found a single 200 mg dose reliably improved choice reaction time (SMD ≈ 0.51) 1Reference 1Gerolymos C et al. · 2026Meta-analysisCognitive and affective effects of L-Theanine: a systematic review and meta-analysis of 31 randomized trials — meta-analysisView study →.
  • Emerging / cautiously endorsed: small improvements in subjective sleep quality and acute stress markers 3,14Reference 3Kimura K et al. · 2007RCTL-Theanine reduces psychological and physiological stress responses — RCT (crossover)View study →Reference 14Bulman A et al. · 2025Meta-analysisThe effects of L-theanine consumption on sleep outcomes: A systematic review and meta-analysisView study →, and adjunctive use in schizophrenia, where 400 mg/day added to antipsychotics reduced anxiety and positive-symptom scores in two RCTs 16,17Reference 16Ritsner MS et al. · 2011RCTL-theanine relieves positive, activation, and anxiety symptoms in patients with schizophrenia and schizoaffective disorder: an 8-week RCTView study →Reference 17Shamabadi A et al. · 2023RCTL-Theanine adjunct to risperidone in the treatment of chronic schizophrenia inpatients — RCTView study →.
  • Popular but thin / overhyped: standalone anxiety relief and antidepressant claims — inconsistent across trials, driven by single studies or high-risk-of-bias data 1,2Reference 1Gerolymos C et al. · 2026Meta-analysisCognitive and affective effects of L-Theanine: a systematic review and meta-analysis of 31 randomized trials — meta-analysisView study →Reference 2Williams JL et al. · 2020Systematic reviewThe Effects of Green Tea Amino Acid L-Theanine Consumption on the Ability to Manage Stress and Anxiety Levels: a Systematic ReviewView study →. Sleep benefits rest largely on branded products, not “pure” L-theanine 14Reference 14Bulman A et al. · 2025Meta-analysisThe effects of L-theanine consumption on sleep outcomes: A systematic review and meta-analysisView study →.
  • The honest miss / caveat: there is no dietary deficiency of L-theanine, so it is never correcting anything — and its most reliable single benefit (attention) is largely inseparable from the caffeine it is usually taken with.
Evidence by indicationStrength of support
Attention & Focus (with Caffeine)Promising
78%
Reaction Time & Attention (alone)Promising
74%
Acute Stress ResponsePromising
58%
Sleep QualityPromising
54%
Schizophrenia (adjunct)Promising
52%
AnxietyShaky
44%
Depressive SymptomsShaky
38%
Stress-Related Blood PressureShaky
34%
1. Attention & focus (with caffeine)

The most robust finding for L-theanine is not the compound alone but its combination with caffeine. In double-blind crossover RCTs, 97 mg L-theanine + 40 mg caffeine improved accuracy on attention-switching tasks and reduced susceptibility to distraction versus placebo 5Reference 5Haskell CF et al. · 2008RCTThe effects of L-theanine, caffeine and their combination on cognition and mood — RCTView study →, and 100 mg L-theanine + 50 mg caffeine improved both speed and accuracy on the attention-switching task while reducing distractibility 6Reference 6Owen GN et al. · 2008RCTThe combined effects of L-theanine and caffeine on cognitive performance and mood — RCTView study →; a further crossover RCT found the combination raised subjective alertness and accuracy on demanding tasks 7Reference 7Giesbrecht T et al. · 2010RCTThe combination of L-theanine and caffeine improves cognitive performance and increases subjective alertness — RCTView study →. A 2025 systematic review and meta-analysis of RCTs in healthy participants found that theanine plus caffeine produced small-to-moderate benefits in cognition and mood within the first two hours, favouring the combination over placebo 10Reference 10Payne ER et al. · 2025Meta-analysisEffects of Tea or its Bioactive Compounds L-Theanine or L-Theanine plus Caffeine on Cognition, Sleep, and Mood in Healthy Participants: Systematic Review and Meta-AnalysisView study →. The typical “stack” is a roughly 2:1 theanine:caffeine ratio. The honest read is that caffeine does much of the cognitive lifting, and theanine’s contribution is chiefly to blunt caffeine’s jitteriness while preserving alertness.

Gap: the benefit is largely inseparable from caffeine — few trials isolate theanine’s own contribution to attention, and doses/ratios vary widely.

2. Reaction time & attention (alone)

Even without caffeine, a single dose of L-theanine improves acute attention. The largest synthesis to date — a 2026 systematic review and meta-analysis of 31 RCTs (n = 1168) — found that a single 200 mg dose taken 30–60 minutes before testing significantly improved choice reaction time (SMD = 0.51; 95% CI 0.25–0.77), consistent with enhanced attention 1Reference 1Gerolymos C et al. · 2026Meta-analysisCognitive and affective effects of L-Theanine: a systematic review and meta-analysis of 31 randomized trials — meta-analysisView study →. A 2025 meta-analysis of cognitive-performance RCTs reached a similarly cautious “promising but not conclusive” verdict 13Reference 13Mátyus RO et al. · 2025Meta-analysisPromising, but Not Completely Conclusive: The Effect of l-Theanine on Cognitive Performance — Systematic Review and Meta-Analysis of RCTsView study →. Effects are most evident on acute, timed attention tasks rather than on memory or executive function, and a 12-week RCT in middle-aged/older adults found only selective cognitive benefits 11Reference 11Baba Y et al. · 2021RCTEffects of l-Theanine on Cognitive Function in Middle-Aged and Older Subjects: A Randomized Placebo-Controlled Study — RCTView study →.

Gap: benefits are acute and task-specific (attention/reaction time), not broad cognitive enhancement, and longer-term dosing data are thin.

3. Acute stress response

L-theanine shows a modest, physiologically plausible anti-stress effect. In an early crossover RCT, 200 mg taken before a mental-arithmetic stressor reduced heart rate and salivary immunoglobulin-A responses, consistent with attenuated sympathetic activation 3Reference 3Kimura K et al. · 2007RCTL-Theanine reduces psychological and physiological stress responses — RCT (crossover)View study →. A systematic review concluded that 200–400 mg/day may help manage stress and anxiety in people exposed to stressful conditions 2Reference 2Williams JL et al. · 2020Systematic reviewThe Effects of Green Tea Amino Acid L-Theanine Consumption on the Ability to Manage Stress and Anxiety Levels: a Systematic ReviewView study →, and a 28-day RCT of a branded 200 mg dose in moderately stressed adults reported improvements with good tolerability 4Reference 4Moulin M et al. · 2024RCTSafety and Efficacy of AlphaWave L-Theanine Supplementation for 28 Days in Healthy Adults with Moderate Stress — RCTView study →. However, the 2026 meta-analysis found the acute-stress effect small (SMD ≈ 0.31) and heavily influenced by high-risk-of-bias studies 1Reference 1Gerolymos C et al. · 2026Meta-analysisCognitive and affective effects of L-Theanine: a systematic review and meta-analysis of 31 randomized trials — meta-analysisView study →.

Gap: effect sizes are small and the cleaner (low-bias) studies show the weakest signal; most positive data are acute, not sustained.

4. Sleep quality

A 2025 systematic review and meta-analysis (19 RCTs, N = 897) found L-theanine significantly improved subjective sleep-onset latency (SMD = 0.15), daytime dysfunction (SMD = 0.33) and overall subjective sleep-quality score (SMD = 0.43) 14Reference 14Bulman A et al. · 2025Meta-analysisThe effects of L-theanine consumption on sleep outcomes: A systematic review and meta-analysisView study →. A 6-week RCT in boys with ADHD using 400 mg/day (Suntheanine) improved objectively measured (actigraphy) sleep efficiency 15Reference 15Lyon MR et al. · 2011RCTThe effects of L-theanine (Suntheanine) on objective sleep quality in boys with ADHD — RCTView study →. The consistent limitation, flagged by the reviewers themselves, is that improvements are subjective and most trials used branded or combination products rather than pure L-theanine, so dose and duration for sleep remain undefined 14Reference 14Bulman A et al. · 2025Meta-analysisThe effects of L-theanine consumption on sleep outcomes: A systematic review and meta-analysisView study →.

Gap: benefits are on subjective scales, effect sizes small, and “pure” L-theanine sleep data are scarce — most evidence comes from branded/combination formulas.

5. Schizophrenia (adjunct)

As an add-on to antipsychotics, L-theanine has two supportive 8-week RCTs. In 60 patients with schizophrenia/schizoaffective disorder, 400 mg/day added to ongoing antipsychotics reduced anxiety (HARS) and positive and general psychopathology (PANSS) scores versus placebo 16Reference 16Ritsner MS et al. · 2011RCTL-theanine relieves positive, activation, and anxiety symptoms in patients with schizophrenia and schizoaffective disorder: an 8-week RCTView study →. A 2023 RCT of 400 mg/day adjunct to risperidone in chronic schizophrenia inpatients reported reductions in negative and general psychopathology scores 17Reference 17Shamabadi A et al. · 2023RCTL-Theanine adjunct to risperidone in the treatment of chronic schizophrenia inpatients — RCTView study →. A 2024 systematic review of L-theanine across mental disorders concluded it reduced psychiatric symptoms more than control in schizophrenia, anxiety disorders and ADHD 18Reference 18Moshfeghinia R et al. · 2024Systematic reviewThe effects of L-theanine supplementation on the outcomes of patients with mental disorders: a systematic reviewView study →.

Gap: trials are small, adjunctive (never monotherapy), and from a limited number of centres; this is a promising signal awaiting larger replication, not established practice.

6. Anxiety

Standalone anxiety relief is the weakest of the widely-marketed claims. The 2026 meta-analysis found anxiety effects inconsistent and non-significant, with the only significant result coming from a single study of psychotic anxiety (SMD = 0.54; 400 mg/day for 8 weeks) 1Reference 1Gerolymos C et al. · 2026Meta-analysisCognitive and affective effects of L-Theanine: a systematic review and meta-analysis of 31 randomized trials — meta-analysisView study →. Systematic reviews suggest 200–400 mg/day may help situational stress/anxiety in people under acute stress 2Reference 2Williams JL et al. · 2020Systematic reviewThe Effects of Green Tea Amino Acid L-Theanine Consumption on the Ability to Manage Stress and Anxiety Levels: a Systematic ReviewView study →, but this is different from a clinical anxiolytic effect in anxiety disorders.

Gap: no consistent effect on clinical anxiety; positive results are situational, small, or confined to specific clinical subgroups.

7. Depressive symptoms

A potential antidepressant effect is intriguing but unconfirmed. The 2026 meta-analysis found that, after excluding one outlier, a single dose produced a significant reduction in depressive symptoms in healthy individuals (SMD = 0.69; 95% CI 0.13–1.25) with low heterogeneity — a finding the authors flagged as warranting confirmation in high-quality trials 1Reference 1Gerolymos C et al. · 2026Meta-analysisCognitive and affective effects of L-Theanine: a systematic review and meta-analysis of 31 randomized trials — meta-analysisView study →. There are no adequately powered RCTs of L-theanine as a treatment for major depressive disorder.

Gap: rests on a single-dose signal in healthy (non-depressed) people; no confirmatory trials in diagnosed depression.

Mechanisms

Target / pathwayEffectRelevant to
Alpha brain-wave activity (EEG)Increases alpha power (relaxed, wakeful attention)Attention, stress, “calm focus”
Glutamate receptors (AMPA/NMDA/kainate)Low-affinity antagonist; glutamate-reuptake modulationAnti-stress, neuroprotection, attention
GABA / GABA-AModest increase / receptor activityRelaxation, anxiety, sleep
Dopamine & serotoninModulates levelsMood, cognition
Sympathetic nervous systemAttenuates stress-induced activation (↓HR, ↓s-IgA)Acute stress, stress-related BP

Pharmacokinetics

L-theanine is well absorbed from the small intestine (an intestinal amino-acid transporter also carries the related glutamate/methionine substrates) and crosses the blood–brain barrier. In humans, plasma concentrations peak roughly 30–60 minutes after an oral dose and the elimination half-life is short — on the order of ~1 hour — which is why acute-attention trials dose 30–60 minutes before testing and why effects are transient rather than cumulative 1Reference 1Gerolymos C et al. · 2026Meta-analysisCognitive and affective effects of L-Theanine: a systematic review and meta-analysis of 31 randomized trials — meta-analysisView study →. The physiologically active enantiomer is L-theanine; animal data show L-theanine is far better absorbed than D-theanine, and that co-administered enantiomers compete for absorption 21Reference 21Enantioselective (L- vs D-) absorption oAnimalhttps://pubmed.ncbi.nlm.nih.gov/15704209/View study →. Because it is cleared quickly and not stored, there is no “loading” — dosing is per-occasion (e.g. before a task or before bed) rather than to build a level.

Clinical trials

L-theanine is an off-patent, inexpensive amino acid, so most trials are small, single-centre, and frequently sponsor-linked to branded ingredients (Suntheanine, AlphaWave); there is little large-scale independent trial activity. Recent meta-analyses now pool 19–50 RCTs, indicating a moderately active but fragmented evidence base.

CompletedPlannedTerminatedPreclinical
~50RCTs (pooled in reviews)Several ongoingFew reportedExtensive(rodent/in vitro)

Last checked: July 2026.

Dietary Sources

Unlike a vitamin or mineral, L-theanine is not an essential nutrient — there is no requirement and no deficiency state. It occurs almost exclusively in the tea plant (Camellia sinensis), which means virtually all dietary L-theanine comes from tea (green, black, white, oolong — all from the same plant) and from the related holly Ilex guayusa. Trace amounts occur in one mushroom, the bay bolete (Imleria badia). It accounts for a large share of the free amino acids in tea leaves and is responsible for tea’s characteristic umami and the “smooth” quality of its stimulation.

SourceTypical L-theanine content
Green/black tea (brewed)~6–25 mg per cup (varies widely with cultivar, shading, and steeping)
Matcha (whole powdered leaf)Higher per serving than steeped tea (whole leaf consumed)
Guayusa (Ilex guayusa)Present; a caffeine-bearing holly used similarly to tea
Bay bolete mushroomTrace

A key practical point: a typical cup of tea supplies only a fraction (often ~10–25 mg) of the 100–400 mg doses used in research, which is why studied effects generally require a supplement rather than beverage consumption. Shade-grown teas (e.g. gyokuro, matcha) are higher in theanine 12,20Reference 12Türközü D · 2017ReviewL-theanine, unique amino acid of tea, and its metabolism, health effects, and safety — reviewView study →Reference 20Dashwood R et al. · 2025Reviewl-theanine: From tea leaf to trending supplement — does the science match the hype for brain health and relaxation? — reviewView study →.

Intake & Dosage

These are doses studied in research, not a personal recommendation.

  • No RDA/AI or Upper Limit: L-theanine is not an essential nutrient, so no reference intake or Tolerable Upper Intake Level has been established. “No UL” means one has not been set — it does not mean unlimited intake is proven safe.
  • Studied supplemental range: most trials use 100–400 mg per dose; a single 200 mg dose 30–60 minutes before a task is the most common acute-attention protocol 1Reference 1Gerolymos C et al. · 2026Meta-analysisCognitive and affective effects of L-Theanine: a systematic review and meta-analysis of 31 randomized trials — meta-analysisView study →. Stress/anxiety systematic reviews describe 200–400 mg/day 2Reference 2Williams JL et al. · 2020Systematic reviewThe Effects of Green Tea Amino Acid L-Theanine Consumption on the Ability to Manage Stress and Anxiety Levels: a Systematic ReviewView study →. Adjunctive psychiatric trials used 400 mg/day 16,17Reference 16Ritsner MS et al. · 2011RCTL-theanine relieves positive, activation, and anxiety symptoms in patients with schizophrenia and schizoaffective disorder: an 8-week RCTView study →Reference 17Shamabadi A et al. · 2023RCTL-Theanine adjunct to risperidone in the treatment of chronic schizophrenia inpatients — RCTView study →.
  • With caffeine: the popular “stack” is roughly 2:1 theanine:caffeine (e.g. 200 mg theanine + 100 mg caffeine), the ratio found to sharpen attention while blunting caffeine jitteriness 6,7Reference 6Owen GN et al. · 2008RCTThe combined effects of L-theanine and caffeine on cognitive performance and mood — RCTView study →Reference 7Giesbrecht T et al. · 2010RCTThe combination of L-theanine and caffeine improves cognitive performance and increases subjective alertness — RCTView study →.
  • Timing, not loading: because the half-life is short (~1 hour) and it is not stored, dosing is per-occasion — before focused work, before a stressor, or before bed — rather than a daily level to build up.
  • Form: only the L-enantiomer is physiologically relevant; commercial supplements (including branded Suntheanine/AlphaWave) are L-theanine. D-theanine is poorly absorbed and not used.

Safety

L-theanine has a strong safety record. Across acute and repeated-dose human trials up to 400 mg/day and toxicology studies, no serious adverse events have been reported, and the 31-RCT meta-analysis found dropout rates and reasons comparable to placebo 1,4Reference 1Gerolymos C et al. · 2026Meta-analysisCognitive and affective effects of L-Theanine: a systematic review and meta-analysis of 31 randomized trials — meta-analysisView study →Reference 4Moulin M et al. · 2024RCTSafety and Efficacy of AlphaWave L-Theanine Supplementation for 28 Days in Healthy Adults with Moderate Stress — RCTView study →. Mild, infrequent effects can include headache or lightheadedness; because it can lower stress-related sympathetic activity and blood-pressure reactivity, very high intakes could theoretically add to the effects of blood-pressure-lowering or sedative agents.

  • Interactions: the most plausible are additive, not toxic — with stimulants/caffeine (intended, generally favourable), with antihypertensive drugs (theoretical additive lowering of stress-related blood pressure) 19Reference 19Yoto A et al. · 2012RCTEffects of L-theanine or caffeine intake on changes in blood pressure under physical and psychological stresses — RCTView study →, and with sedatives/CNS depressants (theoretical additive calming). In psychiatric trials it was safely combined with antipsychotics (risperidone) 16,17Reference 16Ritsner MS et al. · 2011RCTL-theanine relieves positive, activation, and anxiety symptoms in patients with schizophrenia and schizoaffective disorder: an 8-week RCTView study →Reference 17Shamabadi A et al. · 2023RCTL-Theanine adjunct to risperidone in the treatment of chronic schizophrenia inpatients — RCTView study →. Separate from or discuss with a prescriber if on blood-pressure or sedative medication.
  • Who should be cautious: anyone on blood-pressure or sedative medication (timing/additive effects), and — as with any supplement — those who are pregnant or breastfeeding (see below).
  • No pharmacokinetic (CYP-mediated) interactions are established, and no UL has been set — absence of a UL is not evidence that unlimited intake is safe.

Pregnancy & lactation

Not established — avoid supplemental doses. There are no adequate human safety trials of supplemental L-theanine in pregnancy or lactation. Ordinary dietary intake from tea is a separate question (tea’s caffeine is the more studied concern in pregnancy), but concentrated 100–400 mg supplement doses have not been evaluated for fetal or infant safety. Pregnant or breastfeeding people should not use L-theanine supplements without discussing it with a qualified practitioner.

References

  1. Gerolymos C, et al. (2026). Cognitive and affective effects of L-Theanine: a systematic review and meta-analysis of 31 randomized trials — meta-analysis. Mol Psychiatry. https://pubmed.ncbi.nlm.nih.gov/42410082/
  2. Williams JL, et al. (2020). The Effects of Green Tea Amino Acid L-Theanine Consumption on the Ability to Manage Stress and Anxiety Levels: a Systematic Review. Plant Foods Hum Nutr. https://pubmed.ncbi.nlm.nih.gov/31758301/
  3. Kimura K, et al. (2007). L-Theanine reduces psychological and physiological stress responses — RCT (crossover). Biol Psychol. https://pubmed.ncbi.nlm.nih.gov/16930802/
  4. Moulin M, et al. (2024). Safety and Efficacy of AlphaWave L-Theanine Supplementation for 28 Days in Healthy Adults with Moderate Stress — RCT. Neurol Ther. https://pubmed.ncbi.nlm.nih.gov/38758503/
  5. Haskell CF, et al. (2008). The effects of L-theanine, caffeine and their combination on cognition and mood — RCT. Biol Psychol. https://pubmed.ncbi.nlm.nih.gov/18006208/
  6. Owen GN, et al. (2008). The combined effects of L-theanine and caffeine on cognitive performance and mood — RCT. Nutr Neurosci. https://pubmed.ncbi.nlm.nih.gov/18681988/
  7. Giesbrecht T, et al. (2010). The combination of L-theanine and caffeine improves cognitive performance and increases subjective alertness — RCT. Nutr Neurosci. https://pubmed.ncbi.nlm.nih.gov/21040626/
  8. Kahathuduwa CN, et al. (2020). Effects of L-theanine-caffeine combination on sustained attention and inhibitory control among children with ADHD — RCT. Sci Rep. https://pubmed.ncbi.nlm.nih.gov/32753637/
  9. Anas Sohail A, et al. (2021). The Cognitive-Enhancing Outcomes of Caffeine and L-theanine: A Systematic Review. Cureus. https://pubmed.ncbi.nlm.nih.gov/35111479/
  10. Payne ER, et al. (2025). Effects of Tea or its Bioactive Compounds L-Theanine or L-Theanine plus Caffeine on Cognition, Sleep, and Mood in Healthy Participants: Systematic Review and Meta-Analysis. Nutr Rev. https://pubmed.ncbi.nlm.nih.gov/40314930/
  11. Baba Y, et al. (2021). Effects of l-Theanine on Cognitive Function in Middle-Aged and Older Subjects: A Randomized Placebo-Controlled Study — RCT. J Med Food. https://pubmed.ncbi.nlm.nih.gov/33751906/
  12. Türközü D, Şanlıer N. (2017). L-theanine, unique amino acid of tea, and its metabolism, health effects, and safety — review. Crit Rev Food Sci Nutr. https://pubmed.ncbi.nlm.nih.gov/26192072/
  13. Mátyus RO, et al. (2025). Promising, but Not Completely Conclusive: The Effect of l-Theanine on Cognitive Performance — Systematic Review and Meta-Analysis of RCTs. J Clin Med. https://pubmed.ncbi.nlm.nih.gov/41227106/
  14. Bulman A, et al. (2025). The effects of L-theanine consumption on sleep outcomes: A systematic review and meta-analysis. Sleep Med Rev. https://pubmed.ncbi.nlm.nih.gov/40056718/
  15. Lyon MR, et al. (2011). The effects of L-theanine (Suntheanine) on objective sleep quality in boys with ADHD — RCT. Altern Med Rev. https://pubmed.ncbi.nlm.nih.gov/22214254/
  16. Ritsner MS, et al. (2011). L-theanine relieves positive, activation, and anxiety symptoms in patients with schizophrenia and schizoaffective disorder: an 8-week RCT. J Clin Psychiatry. https://pubmed.ncbi.nlm.nih.gov/21208586/
  17. Shamabadi A, et al. (2023). L-Theanine adjunct to risperidone in the treatment of chronic schizophrenia inpatients — RCT. Psychopharmacology (Berl). https://pubmed.ncbi.nlm.nih.gov/37697164/
  18. Moshfeghinia R, et al. (2024). The effects of L-theanine supplementation on the outcomes of patients with mental disorders: a systematic review. BMC Psychiatry. https://pubmed.ncbi.nlm.nih.gov/39633316/
  19. Yoto A, et al. (2012). Effects of L-theanine or caffeine intake on changes in blood pressure under physical and psychological stresses — RCT. J Physiol Anthropol. https://pubmed.ncbi.nlm.nih.gov/23107346/
  20. Dashwood R, et al. (2025). l-theanine: From tea leaf to trending supplement — does the science match the hype for brain health and relaxation? — review. Nutr Res. https://pubmed.ncbi.nlm.nih.gov/39854799/
  21. Enantioselective (L- vs D-) absorption of theanine in rats — animal pharmacokinetic study. https://pubmed.ncbi.nlm.nih.gov/15704209/