L-Theanine for Attention and ADHD: What Trials Found
What small trials found for L-theanine, alone or with caffeine, on attention and in children with ADHD, why healthy-adult results do not transfer, and why it is not a treatment.
Content last updated . This page has not been medically reviewed.
Quick answer
For ADHD, Proper evidence not found for large, long trials showing that L-theanine improves attention or core ADHD symptoms. We searched PubMed for theanine with ADHD, attention and cognition and found a handful of small studies, one with only five boys. [1] A 2024 systematic review of 11 trials in people with mental health conditions, which included ADHD, reported fewer psychiatric symptoms than control conditions but said more studies were needed to validate the findings. [2] L-theanine is not a replacement for assessment or treatment. This page is information only.
How the evidence is labeled
Promising but limited means small studies point one way. Mixed means results differ by task or study. Insufficient evidence means too few trials to judge. A short laboratory task is not the same as everyday school or work performance, and results from healthy adults do not tell us what happens in ADHD.Trials in children and teens with ADHD
| Study | What it found | Strength of evidence |
|---|---|---|
| Boys 8-15 with ADHD, single doses | In a four-way crossover with five boys, L-theanine (2.5 mg per kg of body weight, a study amount), caffeine (2.0 mg per kg), both together and placebo were compared. L-theanine improved a total cognition score; caffeine worsened inhibitory control; the combination improved the cognition score and a Go/NoGo accuracy measure. [1] | Insufficient evidence (five boys, one dose, "proof-of-concept") |
| Boys 8-12 with ADHD, 6 weeks | In 98 boys with a confirmed ADHD diagnosis, actigraph-measured sleep percentage and sleep efficiency were higher with L-theanine than placebo; sleep latency and other sleep measures did not change. [3] The outcome was sleep, not attention or behavior. | Promising but limited, for sleep only |
| Parent-reported sleep | In the same trial, parents' questionnaire answers did not correlate significantly with the actigraph data. [3] | Shows limits of parent ratings |
| Mental health review | The 11-trial review found lower psychiatric symptoms with L-theanine in schizophrenia, anxiety disorders and ADHD, with confirmation still needed. [2] The abstract does not say how many trials were in ADHD. | Promising but limited |
In the 98-boy trial, randomization was stratified by current stimulant use, so some boys were already taking stimulant medicine. [3] L-theanine was reported as well tolerated with no significant adverse events over six weeks. [3]
Trials in healthy adults (not ADHD)
| Study | What it found | Strength of evidence |
|---|---|---|
| Young adults (44), theanine plus caffeine | In a placebo-controlled trial of 97 mg theanine with 40 mg caffeine (a study amount), task-switching accuracy and self-rated alertness improved; there were no significant effects on visual search, choice reaction time or mental rotation. [4] | Mixed |
| Healthy volunteers (27), caffeine with and without theanine | Combination improved speed and accuracy on an attention-switching task at 60 minutes compared with placebo; caffeine alone helped alertness. [5] | Promising but limited |
| Meta-analysis of 50 trials | Small differences favoring theanine plus caffeine on some attention and mood tasks, but the confidence intervals often show uncertainty about size and direction. [6] | Mixed |
| Sleep-deprived young adults, theanine alone | In 24 volunteers, theanine reduced false alarms on a traffic-scene task, but the change in reaction time was not significantly different from placebo. [7] | Promising but limited |
| Sleep-deprived young adults, theanine plus caffeine | In 37 volunteers, the combination improved the hit rate on a similar task. [8] | Promising but limited |
| Memory supplements review | A 2023 review of over-the-counter memory supplements found no compelling evidence for L-theanine for memory. [9] | No good evidence for memory |
The combination trials above used caffeine as well. Caffeine has its own effects and risks; see Caffeine Plus L-Theanine and Multicomponent "Brain" Formulas. Results for sleep-deprived adults do not apply to people who are well rested, to children, or to people with ADHD.
What official sources say about treating ADHD
The NHS says ADHD medicines must be started and monitored by an ADHD specialist, that not everyone with ADHD needs or wants medicine, and that lifestyle steps, school and home support and sometimes talking therapies are part of care. [10] The NIMH describes standard treatments as medication and psychosocial interventions such as cognitive behavioral therapy, parent training and school interventions. [11] Neither page we read mentions L-theanine.Where to go next
ADHD in Adults · Supplements for ADHD: What Trials Found · Focus and Memory · Nootropic Evidence by OutcomeFrequently asked questions
Does L-theanine help ADHD?
Proper evidence not found for large trials. The studies we read were small: five boys in a single-dose study, [1] and a 98-boy trial whose measured result was better sleep, not attention. [3] A review reported benefit across several conditions including ADHD and called for more studies. [2]
Can L-theanine replace ADHD medicine?
No source we read says so, and the NHS and NIMH pages we read do not mention L-theanine. ADHD medicines are started and monitored by a specialist, [10] and you should not stop or change a prescribed medicine without talking to your prescriber.
Does L-theanine improve focus in healthy people?
Some short lab tasks improved with theanine plus caffeine, others did not, and a meta-analysis found uncertain differences. [4][6] Lab tasks are not everyday performance.
Is L-theanine safe for children?
The 6-week trial in boys with ADHD reported no significant adverse events, [3] but it was one trial of limited length. A pediatrician can advise on any supplement for a child.
What does theanine do for memory?
A 2023 review found no compelling evidence for L-theanine for memory. [9]
More details: evidence, limits and cautions
The details behind this page: cautions, limits of the evidence and where sources disagree. Open any note to read it.
Safety and who should ask first
- Do not change prescribed ADHD medicine on your own. Tell the prescriber and pharmacist about any supplement. Prescription stimulants and supplements are not interchangeable; see Prescription ADHD Stimulants vs Supplements.
- Children and teens: talk with a pediatrician first. The trials above were short, in small groups.
- Caffeine in the combination: the five-boy study found caffeine worsened a measure of inhibitory control. [1]
- Pregnancy, kidney or liver conditions, medicines, pre-surgery: see L-Theanine Side Effects, Interactions and Who Should Ask First.
- Product quality: see Quality Testing and Certifications.
References
- Kahathuduwa CN et al., Effects of L-theanine-caffeine combination on sustained attention and inhibitory control among children with ADHD: a proof-of-concept neuroimaging RCT. Sci Rep 2020. Read 2026-10-23.
- Moshfeghinia R et al., The effects of L-theanine supplementation on the outcomes of patients with mental disorders: a systematic review. BMC Psychiatry 2024. Read 2026-10-23.
- Lyon MR et al., The effects of L-theanine on objective sleep quality in boys with attention deficit hyperactivity disorder (ADHD): a randomized, double-blind, placebo-controlled clinical trial. Altern Med Rev 2011. Read 2026-10-23.
- Giesbrecht T et al., The combination of L-theanine and caffeine improves cognitive performance and increases subjective alertness. Nutr Neurosci 2010. Read 2026-10-23.
- Owen GN et al., The combined effects of L-theanine and caffeine on cognitive performance and mood. Nutr Neurosci 2008. Read 2026-10-23.
- Payne ER et al., Effects of tea or its bioactive compounds l-theanine or l-theanine plus caffeine on cognition, sleep, and mood in healthy participants: a systematic review and meta-analysis of randomized controlled trials. Nutr Rev 2025. Read 2026-10-23.
- Karunaratne UW, Dassanayake TL, Effect of L-theanine on selective attention in a traffic-related reaction task in sleep-deprived young adults. Nutr Neurosci 2025. Read 2026-10-23.
- Karunaratne UW et al., High-dose L-theanine-caffeine combination improves neurobehavioural and neurophysiological measures of selective attention in acutely sleep-deprived young adults. Br J Nutr 2025. Read 2026-10-23.
- Hersant H et al., Over the counter supplements for memory: a review of available evidence. CNS Drugs 2023. Read 2026-10-23.
- NHS (UK), ADHD in children and young people (page last reviewed 19 March 2025) Read 2026-10-23.
- National Institute of Mental Health (US), Attention-Deficit/Hyperactivity Disorder Read 2026-10-23.
Education, not medical advice. This page is for general information. It does not diagnose or treat any condition and is not a substitute for care from a qualified health professional. Natural does not automatically mean safe. Ask a clinician or pharmacist before changing your care, especially if you take medication, are pregnant or breastfeeding, or have a health condition.