L-Theanine and Reduced Anxiety

Research synthesisLow evidenceSmall effect6 studies · 2 beneficial · 4 neutral · 0 harmful

Across 6 studies, 2 found beneficial moderate-sized effects on anxiety reduction, while 4 found no significant benefit (neutral, small effect size). The predominant direction is neutral, with most studies using doses of 200–400 mg/day in varied populations (e.g., clinical GAD, athletes, children). One 70-day RCT reported no effect; evidence does not support a consistent anxiolytic benefit.

Caveats: Many of the included studies (4 of 6) did not reach statistical significance — effect may be smaller than the predominant direction suggests. The two beneficial studies are a systematic review and a narrative review, while the neutral studies include several RCTs with higher evidence scores. Study durations are poorly reported; the only long-term trial (70 days) showed no benefit.

Generated Jul 12, 2026

Doses used in studies

mg/day: 200–900 (median 300, IQR 200–650) — 3 studies
mg/kg/day: 3 (median 3, IQR 3–3) — 1 study

Time to effect

Median: 10 weeks · IQR 10 weeks–10 weeks · Range 10 weeks–10 weeks — Reported in 1 of 6 studies

Safety in these studies

Overall tolerabilityReported
Most of these treatments have shown at least some efficacy.
from: New and emerging treatments for anxiety disorders.

6 of 6 papersPopulation:

L-theanine in the adjunctive treatment of generalized anxiety disorder: A double-blind, randomised, placebo-controlled trial.
- 2019-03
- RCT · n = 46
- Journal of psychiatric research 110
- - Jerome Sarris
  - Gerard J Byrne
  - Lachlan Cribb
  - Georgina Oliver
  - Jenifer Murphy
  - Patricia Macdonald
  - Sonia Nazareth
  - Diana Karamacoska
  - Samantha Galea
  - Anika Short
  - Carolyn Ee
  - Yoann Birling
  - Ranjit Menon
  - Chee H Ng
- PubMed: 30580081
- DOI: 10.1016/j.jpsychires.2018.12.014
7 Insights on
- Reduced Anxiety
- High evidence
- Clinical
Results revealed that adjunctive L-theanine did not outperform placebo for anxiety reduction on the HAMA (p = 0.73)
Effect
Neutral
Effect size
Small
Significant
No
Dose
450-900 mg
Performance-enhancing effects of caffeine and L-Theanine among Iranian elite wrestlers: a focus on cognitive and specific physical performance.
- 2025-09-22
- RCT
- Journal of the International Society of Sports Nutrition 22(1)
- - Rouzbeh Razazan
  - Mohammad Hemmatinafar
  - Babak Imanian
  - Nima Jahaniboushehri
  - Rasoul Rezaei
  - Gholamhossein Nazemzadegan
- PubMed: 40977612
- DOI: 10.1080/15502783.2025.2564238
9 Insights on
- Reduced Anxiety
- High evidence
- Athletes
CAF+THE reduced anxiety to below placebo levels (8% incidence vs 33%).
Effect
Neutral
Effect size
Small
Significant
No
Dose
3 mg/kg
Use of Nutritional Supplements Based on L-Theanine and Vitamin B6 in Children with Tourette Syndrome, with Anxiety Disorders: A Pilot Study.
- 2022-02-18
- RCT · n = 34
- Nutrients 14(4)
- - Renata Rizzo
  - Adriana Prato
  - Miriam Scerbo
  - Federica Saia
  - Rita Barone
  - Paolo Curatolo
- PubMed: 35215501
- DOI: 10.3390/nu14040852
2 Insights on
- Reduced Anxiety
- High evidence
- Rigorous Journal
- Clinical
Between-group differences in clinician-rated severity did reach statistical significance only for tics.
Effect
Neutral
Effect size
Small
Significant
No
The Effects of Green Tea Amino Acid L-Theanine Consumption on the Ability to Manage Stress and Anxiety Levels: a Systematic Review.
- 2019-11-22
- Systematic Review
- Plant foods for human nutrition (Dordrecht, Netherlands) 75(1)
- - Jackson L Williams
  - Julian M Everett
  - Nathan M D'Cunha
  - Domenico Sergi
  - Ekavi N Georgousopoulou
  - Richard J Keegan
  - Andrew J McKune
  - Duane D Mellor
  - Nicola Anstice
  - Nenad Naumovski
- PubMed: 31758301
- DOI: 10.1007/s11130-019-00771-5
2 Insights on
- Reduced Anxiety
- High evidence
supplementation of 200-400 mg/day of L-THE may assist in the reduction of stress and anxiety in people exposed to stressful conditions.
Effect
Beneficial
Effect size
Moderate
Significant
Yes
Dose
200-400 mg/day
Impact of L-theanine and L-tyrosine on markers of stress and cognitive performance in response to a virtual reality based active shooter training drill.
- 2024-07-08
- RCT · n = 28
- Stress (Amsterdam, Netherlands) 27(1)
- - Matthew J McAllister
  - M Hunter Martaindale
  - Courtney C Dillard
  - Rory McCullough
- PubMed: 38975711
- DOI: 10.1080/10253890.2024.2375588
5 Insights on
- Reduced Anxiety
- High evidence
- Adults
Ingestion of L-theanine and L-tyrosine did not impact markers of stress.
Effect
Neutral
Effect size
Small
Significant
No
Dose
200 mg
New and emerging treatments for anxiety disorders.
- 2026-03-16
- Review
- BMJ (Clinical research ed.) 392
- - Tomislav D Zbozinek
  - Sahib S Khalsa
  - Michelle G Craske
- PubMed: 41839508
- DOI: 10.1136/bmj-2024-083441
1 Insight on
- Reduced Anxiety
- Low evidence
Novel stand-alone treatments include … natural supplements-including ashwagandha and L-theanine. … Most of these treatments have shown at least some efficacy.
Effect
Beneficial
Effect size
Moderate
Significant
Yes

L-Theanine and Reduced Anxiety

L-theanine in the adjunctive treatment of generalized anxiety disorder: A double-blind, randomised, placebo-controlled trial.

Performance-enhancing effects of caffeine and L-Theanine among Iranian elite wrestlers: a focus on cognitive and specific physical performance.

Use of Nutritional Supplements Based on L-Theanine and Vitamin B6 in Children with Tourette Syndrome, with Anxiety Disorders: A Pilot Study.

The Effects of Green Tea Amino Acid L-Theanine Consumption on the Ability to Manage Stress and Anxiety Levels: a Systematic Review.

Impact of L-theanine and L-tyrosine on markers of stress and cognitive performance in response to a virtual reality based active shooter training drill.

New and emerging treatments for anxiety disorders.