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Evidence-Based Supplement Research
Evidence-Based Supplement Research
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L-Theanine and Reduced Anxiety

Research synthesisLow evidenceMixed effect size6 studies · 2 beneficial · 4 neutral · 0 harmful

Across 6 studies on L-theanine for reduced anxiety, 2 reported beneficial effects while 4 found neutral results, with no harmful effects observed. The predominant effect size among beneficial studies was moderate, but overall evidence is mixed and inconclusive. The most studied dose range was 200–900 mg/day, and effects were typically examined in clinical populations (e.g., generalized anxiety disorder, Tourette syndrome) with a median study duration of 70 days, though only 1 of 6 studies reported duration.

  • Effective dose range: 200-900 mg/day
  • Studied populations: clinical (generalized anxiety disorder, Tourette syndrome with anxiety)

Caveats: Many of the included studies did not reach statistical significance — effect may be smaller than the predominant direction suggests. Evidence base is small (only 6 studies) — conclusions should be considered preliminary. The only long-term study (70 days) found no benefit over placebo in GAD patients, while shorter and less rigorous studies reported moderate benefits. Most studies lacked form data, so no conclusions can be drawn about specific supplement forms.

Generated Jun 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
6 of 6 papers
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