L-Theanine For Anxiety Clinical Evidence

Last updated: October 4, 2026 - Reviewed by Verdant Wellness Editorial Team

RD

By Gabriela Mitchell, Registered Dietitian (Linkedin)

Last Updated July 2026  ·  22 min read

10% off · weekly tips

Real science on cortisol, stress, and sleep.

Send it →

---

Quick answer: Clinical research shows L-theanine may reduce stress-related anxiety symptoms at 200–400 mg/day, but the evidence for treating diagnosed anxiety disorders like GAD remains inconsistent and largely non-significant. Here is a complete breakdown of every major human trial and systematic review.

---

Table of Contents

1. What Is L-Theanine and Why Is It Being Studied for Anxiety?
2. How L-Theanine Works: The Proposed Anxiolytic Mechanisms
3. Summary of the Clinical Evidence at a Glance
4. Key Human Trials and Systematic Reviews Explained
5. L-Theanine for Generalized Anxiety Disorder: What the GAD Trial Found
6. 2024–2025 Research Updates: What the Newest Reviews Say
7. Dosing, Safety, and How Long Studies Have Run
8. Common Questions Answered by the Clinical Literature
9. L-Theanine vs. Other Anxiolytic Approaches: Context for the Evidence
10. What the Evidence Does and Does Not Support
11. Bottom Line

---

What Is L-Theanine and Why Is It Being Studied for Anxiety?

L-theanine is a non-protein amino acid found almost exclusively in the leaves of Camellia sinensis — the plant that produces green, black, white, and oolong tea. It accounts for a significant portion of the free amino acid content in brewed tea and is widely credited with producing what tea drinkers describe as a calm, focused alertness that differs meaningfully from the jitteriness sometimes associated with caffeine alone.

Over the past two decades, this reputation for producing theanine calm without sedation has driven a surge in supplement sales and a parallel increase in formal scientific investigation. L-theanine anxiety research has moved from animal pharmacology studies in the early 2000s through to human randomized controlled trials and multi-study systematic reviews, particularly between 2019 and 2025.

The compound is now one of the most commercially successful single-ingredient supplements in the anxiety and stress category. That commercial prominence, however, has outpaced the clinical evidence base — a tension that sits at the heart of nearly every peer-reviewed review published in the last several years.

Understanding precisely what the human trials have measured, how they have been designed, what populations they have enrolled, and what their results actually show is essential for anyone trying to answer the question honestly: does L-theanine reduce anxiety?

The answer, as the evidence below will demonstrate, depends heavily on what type of anxiety you are discussing.

---

★★★★★ 4.8 · 1,247 reviews

Feel Calm By Bedtime. Focused By Morning.

Adaptogen-based formula. Third-party tested. Made in an FDA-registered facility. Backed by a 60-day money-back guarantee.

Shop Cortisol Drops →

✓ 60-day guarantee ✓ Free shipping $40+ ✓ Ships in 24hrs

How L-Theanine Works: The Proposed Anxiolytic Mechanisms

Before examining the clinical data, it is worth briefly reviewing the biological mechanisms that researchers have proposed to explain why L-theanine might function as a theanine anxiolytic in humans.

GABA Modulation

L-theanine is structurally similar to glutamate, an excitatory neurotransmitter, and to gamma-aminobutyric acid (GABA), the primary inhibitory neurotransmitter in the central nervous system. Preclinical studies suggest that L-theanine may upregulate GABA activity and influence glycine receptor function, contributing to anxiolytic-like behavior in animal models.

Glutamate Receptor Antagonism

L-theanine appears to act as a partial antagonist at NMDA glutamate receptors and may inhibit the reuptake of glutamate in the synapse. Because excessive glutamatergic activity is associated with anxiety and hyperarousal states, this mechanism is considered a plausible pathway for anxiety reduction.

Alpha Brain Wave Enhancement

Electroencephalography (EEG) studies — including some of the earliest human trials — consistently show that oral L-theanine doses of 50–200 mg increase alpha-band (8–14 Hz) oscillations in the brain within 30–60 minutes of ingestion. Alpha waves are associated with relaxed wakefulness, a state distinct from sleep but also distinct from anxious hyperarousal.

Cortisol and HPA Axis Effects

Some human trials have used salivary cortisol as an objective biomarker and found that L-theanine attenuates cortisol rises in response to stressors. This suggests a possible modulatory effect on the hypothalamic-pituitary-adrenal (HPA) axis, which governs the physiological stress response.

Interaction With Caffeine

Many early positive findings in L-theanine anxiety research used a combined L-theanine and caffeine preparation rather than L-theanine alone. This distinction is important when interpreting the isolated anxiolytic literature, as caffeine and theanine have opposing effects on several neurological pathways and the combination may produce outcomes neither compound achieves independently.

These mechanisms are plausible and supported by preclinical data. The critical question is whether they translate into clinically meaningful anxiety reductions in humans at doses that can be practically consumed — and that is precisely what the clinical trial literature attempts to answer.

Summary of the Clinical Evidence at a Glance

| Study / Review | Year | Design | N | Dose | Duration | Anxiety Outcome | |---|---|---|---|---|---|---| | Systematic review (PubMed 31758301) | 2019 | Systematic review of 9 RCTs | ~234 | 200–400 mg/day | Variable | Likely beneficial for stress/anxiety in stressful conditions; larger studies needed | | 5-RCT human-trials review | 2019 | Systematic review | 104 | 200–400 mg/day | Up to 8 weeks | 4/5 studies showed significant improvement; 1 alprazolam-comparator showed no effect | | GAD randomized controlled trial | 2019 | RCT (adjunctive) | Not disclosed | 400 mg/day | 8 weeks | No significant effect (HAMA p = 0.73) | | 2024 systematic review | 2024 | Systematic review | Mixed | Variable | Variable | Significant reduction in psychiatric symptoms across anxiety, schizophrenia, ADHD — evidence inconsistent | | 2025 PubMed cognitive/affective review | 2025 | Systematic review | Mixed | 400 mg/day (best result) | 8 weeks | Inconsistent; one positive psychotic-anxiety finding (SMD = 0.54) | | 2024 marketing vs. science review | 2024 | Narrative/systematic | Mixed | Variable | Variable | Inconsistent; did not outperform placebo in at least one network meta-analysis |

Key takeaway from the table: Positive findings cluster around stress-related and situational anxiety in non-clinical populations. Findings in diagnosed anxiety disorders — particularly GAD — are largely non-significant.

Key Human Trials and Systematic Reviews Explained

The 2019 Systematic Review: Nine RCTs and a Measured Conclusion

The most frequently cited piece of l-theanine anxiety evidence in the current literature comes from a 2019 systematic review published and indexed on PubMed (PMID 31758301), with a corresponding article available via ScienceDirect. Researchers identified nine peer-reviewed human randomized controlled trials meeting inclusion criteria for L-theanine's effects on stress and anxiety.

The review's conclusion was carefully worded: 200–400 mg/day of L-theanine may help reduce stress and anxiety in stressful situations, but the authors were explicit that larger, longer, and more methodologically rigorous studies are still needed before firm clinical recommendations can be made.

This is an important nuance. The phrase "stressful situations" is not synonymous with "anxiety disorder." Most of the included trials examined acute or sub-acute stress responses in healthy adults — not individuals with a clinical diagnosis of an anxiety disorder. The distinction shapes the entire interpretation of the evidence base.

The 5-RCT Human Trials Review: 104 Participants, 4 Positive Findings

A companion analysis examining human clinical trials specifically — rather than all research designs — identified five RCTs totaling approximately 104 participants. Trials used doses of 200–400 mg/day and ran for up to eight weeks. Four of the five studies reported statistically significant improvements in stress and anxiety outcome measures.

The exception was notable: one study that compared L-theanine directly against alprazolam (a benzodiazepine anxiolytic commonly prescribed for anxiety) found no significant anxiolytic effect for either treatment in that specific comparison context. This finding is sometimes cited selectively to argue L-theanine "works as well as a benzo," but the accurate reading is that neither compound produced a significant effect in that particular trial design — a very different conclusion.

This body of work collectively constitutes what most researchers now refer to when they discuss theanine anxiety clinical findings through 2019.

Outcome Measures Used Across Trials

Understanding which measurement tools these trials employed helps contextualize how "anxiety" was being assessed:

• HAMA (Hamilton Anxiety Rating Scale): A clinician-administered scale used in the GAD trial and several others. Validated for diagnosable anxiety disorders.
• STAI (State-Trait Anxiety Inventory): A widely used self-report scale separating "state" (situational) and "trait" (dispositional) anxiety. Used in several positive studies.
• VAS (Visual Analogue Scale): A simple self-rating scale for subjective states including anxiety, tension, and calmness. Used in several acute-stress studies.
• Salivary cortisol: An objective biomarker of physiological stress. Used in several studies as a secondary endpoint.
• Heart rate variability (HRV) and blood pressure: Autonomic markers used alongside subjective anxiety scales in some trials.

The heterogeneity of outcome measures across trials is one reason systematic reviewers consistently flag that pooled conclusions are difficult to draw with confidence.

★★★★★ 4.8 · 1,247 reviews

The Adaptogens Your Nervous System Has Been Missing.

Ashwagandha, rhodiola, and phosphatidylserine — clinically-studied ingredients that support healthy cortisol rhythms.

Shop Cortisol Drops →

✓ 60-day guarantee ✓ Free shipping $40+ ✓ Ships in 24hrs

L-Theanine for Generalized Anxiety Disorder: What the GAD Trial Found

Of all the evidence reviewed here, the 2019 GAD randomized controlled trial deserves the most detailed attention, because it is the only published trial specifically targeting individuals with a formal diagnosis of generalized anxiety disorder using adjunctive L-theanine at a controlled dose.

Study Design

The trial was a randomized, double-blind, placebo-controlled design examining L-theanine as an adjunctive (add-on) therapy for patients with GAD who were already receiving standard treatment. Participants received 400 mg/day of L-theanine for eight weeks.

Results on Anxiety

The primary anxiety outcome — measured using the Hamilton Anxiety Rating Scale (HAMA) — showed no statistically significant difference between the L-theanine group and the placebo group at study endpoint.

The p-value for the HAMA comparison was p = 0.73, meaning there was essentially no statistical signal of a treatment effect. A p-value of 0.73 is not "almost significant" or "trending toward significance." It represents a near-complete absence of differentiation between the active treatment and placebo.

Results on Insomnia

A secondary outcome — insomnia severity — also showed no significant difference between groups, with p = 0.35.

What This Finding Means for L-Theanine GAD Evidence

The GAD trial is the most direct test of the hypothesis that L-theanine is effective for l-theanine GAD management. Its null result does not mean L-theanine has no biological activity whatsoever — but it strongly suggests that whatever alpha-wave enhancement or GABA modulation occurs at the neurophysiological level does not translate into a clinically meaningful reduction in GAD symptoms as measured by a validated clinical scale.

This is a meaningful and sobering data point for anyone considering L-theanine as a treatment for diagnosed generalized anxiety disorder.

The Adjunctive Design Caveat

It is fair to note that the adjunctive design — where L-theanine was added onto existing treatment — could theoretically obscure modest benefits if the existing treatment was producing a ceiling effect on anxiety reduction. However, this concern cuts both ways: it also means the trial was not testing L-theanine against no treatment at all, and the null result in a clinically motivated population remains relevant.

2024–2025 Research Updates: What the Newest Reviews Say

The 2024 Systematic Review: Promising but Inconsistent

A 2024 systematic review examined L-theanine supplementation across multiple psychiatric populations, including individuals with schizophrenia, anxiety disorders, and ADHD. The review reported that L-theanine supplementation was associated with significantly reduced psychiatric symptoms more effectively than control conditions across these populations as a combined finding.

However — and this is critical — the review's authors noted that the broader evidence base remains mixed and inconsistent. The positive finding at the aggregate level was driven partly by populations with psychotic-spectrum disorders, not solely by anxiety disorder participants.

This is consistent with what the earlier literature showed: effects appear most robust in populations with psychotic anxiety or schizophrenia-spectrum disorders, where the 2025 PubMed review's one positive finding (SMD = 0.54 for psychotic anxiety, 400 mg/day for 8 weeks) sits.

The 2025 Systematic Review on Cognitive and Affective Effects

A 2025 systematic review titled Cognitive and Affective Effects of L-Theanine published on PubMed examined the full scope of cognitive and mood-related research on L-theanine. For anxiety specifically, the review characterized the evidence as inconsistent and largely non-significant across the literature as a whole.

The one standout positive finding in this review was the psychotic-anxiety data point already mentioned: SMD = 0.54 at 400 mg/day over 8 weeks. An SMD (standardized mean difference) of 0.54 represents a moderate effect size, which is genuinely meaningful — but it is specific to a psychotic-anxiety population and should not be generalized to all anxiety presentations.

For general anxiety and stress, the 2025 review's characterization of inconsistent, non-significant effects aligns closely with the 2019 GAD trial's null finding and with the broader pattern observed across the systematic review literature.

The 2024 "Science vs. Marketing" Review

Perhaps the most pointed recent contribution to the l-theanine anxiety evidence debate comes from a 2024 review explicitly framing its inquiry around whether the science matches the marketing for L-theanine supplements. The review concluded that:

1. Findings on anxiety and stress are often inconsistent across the published literature.
2. L-theanine did not outperform placebo in at least one network meta-analysis of herbal treatments for anxiety disorders.
3. The commercial narrative around L-theanine as a proven anxiety remedy substantially outpaces what the clinical trial data actually supports.

This is not a fringe academic critique — it reflects a mainstream evidence appraisal perspective that researchers in psychopharmacology, clinical nutrition, and evidence-based medicine would broadly recognize as accurate.

Where Does the 2024–2025 Literature Leave Us?

The 2024–2025 evidence update is consistent in its messaging: L-theanine is characterized as promising for stress-related symptoms but not a proven stand-alone treatment for diagnosed anxiety disorders. The research community appears to have converged on this distinction, and it is one that consumers, clinicians, and supplement manufacturers would benefit from understanding clearly.

Dosing, Safety, and How Long Studies Have Run

What Doses Have Been Used in Clinical Trials?

Across the theanine anxiety clinical research literature, the dose range studied in human trials is relatively narrow: 200–400 mg/day. This is notably higher than the amount of L-theanine typically consumed in a cup of green tea (approximately 25–60 mg per cup), meaning that most clinical findings cannot be attributed to tea-drinking alone.

The most commonly used dose in trials demonstrating positive findings on theanine anxiety reduction appears to be 200 mg, either as a single acute dose or as a daily supplement. The GAD trial — which found no effect — used 400 mg/day, the upper end of the studied range.

Single Dose vs. Chronic Use

An important distinction in the l-theanine anxiety study literature is between:

• Acute dosing studies: Where a single dose is administered and outcomes are measured within hours. These studies frequently find significant effects on alpha brain waves, self-reported calmness (VAS scales), and acute cortisol responses to laboratory stressors. They represent the strongest signal in the literature.
• Chronic supplementation studies: Where participants take L-theanine daily for weeks (typically 4–8 weeks) and outcome measures reflect cumulative change. These studies show more mixed results, with the GAD trial being the most rigorous example of a null finding.

This pattern — stronger acute effects, weaker chronic effects in clinical populations — is itself a meaningful finding. It suggests L-theanine may function more as an acute l-theanine stress anxiety modulator than a sustained anxiolytic treatment.

Safety Profile

The safety data across the clinical trial literature is reassuring. Studies running up to 8 weeks at 200–400 mg/day have not identified significant adverse effects. L-theanine does not appear to cause:

• Sedation (a key differentiator from benzodiazepines and some herbal anxiolytics like valerian)
• Dependence or withdrawal
• Significant drug interactions (though see the medication combination question below)
• Cognitive impairment

The 2019 clinical review explicitly concluded that 200–400 mg/day for up to 8 weeks is generally safe while acknowledging that longer-term safety data in clinical populations remains limited.

What the Research Does Not Tell Us About Safety

Notably absent from the published literature:

• Long-term safety data beyond 8–12 weeks in any systematic form
• Safety data in pregnant or breastfeeding individuals
• Rigorous drug interaction studies with anxiolytics, antidepressants, or antipsychotics
• Dose-ranging studies above 400 mg/day

★★★★★ 4.8 · 1,247 reviews

See Why Athletes And Executives Take It Daily.

Adaptogen-based formula, third-party tested, made in the USA. Cancel subscription anytime.

Shop Cortisol Drops →

✓ 60-day guarantee ✓ Free shipping $40+ ✓ Ships in 24hrs

Common Questions Answered by the Clinical Literature

Does L-theanine actually reduce anxiety, or only stress?

This is arguably the most important question in the entire literature, and the evidence suggests the answer is: primarily stress, with limited evidence for clinical anxiety.

The studies showing the strongest effects on anxiety-like outcomes have predominantly enrolled healthy adults under experimental stress conditions — not individuals with diagnosed anxiety disorders. The one high-quality trial in diagnosed GAD patients found no significant effect. For the purposes of theanine anxiety reduction, the distinction between stress reactivity in healthy people and anxiety disorder treatment is not semantic — it is clinically fundamental.

What dose of L-theanine is used in clinical studies for anxiety?

The standard dose across l-theanine anxiety study designs is 200–400 mg/day. Most positive findings cluster at 200 mg for acute stress outcomes. The GAD trial used 400 mg/day without finding a significant effect.

Is L-theanine effective for generalized anxiety disorder?

Based on the current evidence, no — or at least, not demonstrably so. The only published RCT directly targeting GAD found no statistically significant effect on the Hamilton Anxiety Rating Scale (p = 0.73). This is the most honest answer the clinical literature can provide at this time.

How fast does L-theanine work for anxiety symptoms?

EEG and subjective rating studies show effects on alpha-wave activity and self-reported calm within 30–60 minutes of a single 100–200 mg dose. These acute effects are the most consistently replicated finding in L-theanine anxiety research. Whether they persist with daily dosing over weeks or represent a sustained treatment benefit is much less clear.

Is L-theanine safe to take daily, and for how long?

Based on available trial data, yes — up to 8 weeks at 200–400 mg/day appears safe for most healthy adults. Beyond 8 weeks, there is simply not enough rigorous human data to characterize long-term safety with confidence.

Can L-theanine be combined with antidepressants or anti-anxiety medications?

The GAD trial used L-theanine as an adjunctive treatment alongside standard therapy, and did not report significant adverse interactions. However, rigorous drug interaction studies have not been conducted. Individuals taking SSRIs, SNRIs, benzodiazepines, or antipsychotics should consult a healthcare provider before adding L-theanine, since pharmacodynamic interactions (particularly additive CNS effects) cannot be ruled out from existing data.

Does L-theanine cause sedation or dependence?

The evidence consistently indicates no sedation at standard doses — a property that distinguishes L-theanine from GABA-active sedatives and from many pharmaceutical anxiolytics. This is one of the compound's genuinely supported properties: it appears to produce relaxation without drowsiness.

There is no published evidence of physical dependence, tolerance development, or withdrawal effects associated with L-theanine use.

Is L-theanine better for situational stress than clinical anxiety disorders?

Yes — this is arguably the most defensible clinical interpretation of the total evidence base. The literature on l-theanine stress anxiety in healthy people under stress conditions is more consistently positive than the literature in diagnosed anxiety populations. If someone is looking for a mild, safe support for situational stress and acute anxiety reactivity, the evidence is more supportive than for chronic anxiety disorder treatment.

What is the difference between L-theanine and caffeine-containing green tea effects?

Many early positive studies used L-theanine combined with caffeine, not L-theanine in isolation. The combination appears to produce effects on attention, calm alertness, and stress responses that may exceed either compound alone. Studies isolating L-theanine without caffeine — which is what most supplements deliver — sometimes show weaker or less consistent effects, though positive findings do exist for L-theanine alone.

Which outcome measures are used in trials?

Studies have used HAMA, STAI (State-Trait Anxiety Inventory), VAS (Visual Analogue Scale), salivary cortisol, EEG alpha-wave measurement, blood pressure, and heart rate variability. The heterogeneity of these measures across trials makes direct comparison difficult and contributes to the "inconsistent" characterization that every major systematic review now applies to the body of l-theanine anxiety evidence.

L-Theanine vs. Other Anxiolytic Approaches: Context for the Evidence

Pharmaceutical Comparators

The one study that directly compared L-theanine to alprazolam (a benzodiazepine) found neither treatment produced a significant anxiolytic effect in that specific design. This is not evidence of equivalence — it may reflect design issues, population characteristics, or dose selection in the trial itself. It would be premature to conclude from this single trial that L-theanine performs as well as a prescribed anxiolytic.

Other Natural Compounds

In a 2024 network meta-analysis of herbal treatments for anxiety disorders referenced in the marketing-versus-science review, L-theanine did not outperform placebo. This positions L-theanine below several other herbal compounds (such as kava, passionflower, and lavender preparations) in terms of clinical evidence strength for anxiety disorder treatment.

Cognitive-Behavioral Therapy (CBT)

For diagnosed anxiety disorders, CBT has far stronger and more consistent evidence than any supplement, including L-theanine. This context does not make L-theanine worthless — it makes the evidence hierarchy clear for clinicians and patients making treatment decisions.

Lifestyle Interventions

Exercise, sleep hygiene, stress management techniques, and dietary approaches have substantial evidence for anxiety-related symptoms. These are complementary to, not replaced by, any supplement-based approach.

What the Evidence Does and Does Not Support

What the Evidence Reasonably Supports

Based on the available theanine anxiety clinical data:

✅ Acute reduction in subjective anxiety and tension in healthy adults exposed to laboratory stressors (consistent finding across multiple studies)

✅ Alpha brain wave enhancement within 30–60 minutes of single-dose administration (robustly replicated neurophysiological finding)

✅ Attenuation of cortisol response to acute psychological stress in some studies (inconsistently replicated, but present in the literature)

✅ Reduction of self-reported stress and anxiety measured via VAS and STAI in short-term studies with healthy participants (4/5 RCTs in the 104-participant systematic review)

✅ General safety at 200–400 mg/day for up to 8 weeks without sedation, dependence, or significant adverse effects

✅ Possible benefit in psychotic anxiety at 400 mg/day over 8 weeks (moderate effect size, SMD = 0.54, in one study)

What the Evidence Does Not Support

❌ Effective treatment for generalized anxiety disorder (null finding in the only dedicated GAD RCT)

❌ Superiority over placebo in network meta-analyses of herbal anxiety disorder treatments

❌ Equivalent or superior performance to pharmaceutical anxiolytics for clinical anxiety

❌ Sustained anxiety reduction over months of daily use (no long-term data)

❌ Efficacy as a standalone treatment for any formally diagnosed anxiety disorder (insufficient evidence)

★★★★★ 4.8 · 1,247 reviews

Ready To Try Adaptogen-Based Cortisol Support?

Third-party tested. 60-day guarantee. Free shipping over $40. Ships in 24 hours.

Shop Cortisol Drops →

✓ 60-day guarantee ✓ Free shipping $40+ ✓ Ships in 24hrs

Bottom Line

The clinical evidence on L-theanine for anxiety tells a story of a genuinely interesting compound whose biological plausibility — alpha-wave enhancement, GABA modulation, HPA axis effects — has generated real scientific interest and a substantial body of human trial data, but whose clinical evidence in anxiety disorders has consistently underdelivered relative to the marketing narrative surrounding it.

Here is what the evidence, fairly summarized, actually says:

L-theanine anxiety research through 2025 shows the compound to be safe, non-sedating, and potentially useful for acute stress-related anxiety in healthy adults. Four out of five RCTs in a systematic review of 104 participants showed improvement in stress and anxiety at 200–400 mg/day. Multiple independent reviews characterize this as "may help reduce stress and anxiety in stressful conditions."

For diagnosed anxiety disorders — particularly GAD — the evidence is not supportive. The dedicated GAD trial found no significant effect (p = 0.73 on HAMA). The 2024 and 2025 systematic reviews characterize the anxiety findings as inconsistent and largely non-significant outside of one psychotic-anxiety population.

The 2024 marketing-versus-science review may offer the most useful frame: L-theanine is a legitimate subject of ongoing scientific inquiry with genuine acute stress-modulating properties, but the gap between the supplement industry's claims and the clinical evidence base for anxiety treatment is real and substantial.

For individuals experiencing situational stress, mild anxiety reactivity, or seeking non-pharmacological support for general wellbeing, L-theanine at 200–400 mg/day represents a low-risk option with a reasonable — if not robust — evidence base.

For individuals with diagnosed generalized anxiety disorder or other clinical anxiety disorders, L-theanine should not be considered a primary treatment. It may be used as part of a broader wellness approach, but should not replace evidence-based treatments including CBT, medication where indicated, and clinical supervision.

The honest answer to "does L-theanine work for anxiety?" is: it depends entirely on what you mean by anxiety, and the evidence for clinical anxiety disorders is not there yet.

References and Source Studies

1. Hidese S, et al. (2019). Effects of L-theanine administration on stress-related symptoms and cognitive functions in healthy adults. Nutrients. PMC6836118.
2. Examined systematic review of 5 RCTs, 104 participants, 200–400 mg/day, up to 8 weeks.
3. ScienceDirect systematic review article: pii/S1043661819307790.
4. PubMed indexed review (PMID 31758301) — 9 human RCT systematic review, 2019.
5. GAD randomized controlled trial (adjunctive L-theanine, 400 mg/day, 8 weeks; HAMA p = 0.73).
6. 2024 systematic review: L-theanine in schizophrenia, anxiety disorders, and ADHD.
7. 2025 systematic review: Cognitive and Affective Effects of L-Theanine (PubMed).
8. 2024 narrative/systematic review: L-theanine: From tea leaf to trending supplement — does the science match the marketing?

This article is for informational purposes only and does not constitute medical advice. If you are experiencing anxiety symptoms, please consult a qualified healthcare professional.