Medicinal herbs for the treatment of anxiety: A systematic review and network meta-analysis.
The one pooled analysis of L-theanine for anxiety found it no better than placebo — if I'm spending money on it monthly, is there something with actual evidence I should try instead?
Well-supported by good-quality research. how we score evidence
Caveat on this rating: A null result across a wide credible interval means "not proven to work", not "proven not to work" — the L-theanine arm of this network rests on few small trials, so a modest real effect cannot be ruled out. The analysis came from a traditional Chinese medicine research institute, which if anything would bias it toward finding herbal benefits, making the null finding for L-theanine harder to dismiss.
L-theanine is sold in the US as a dietary supplement under the Dietary Supplement Health and Education Act of 1994 (DSHEA), and as a food additive it holds Generally Recognized as Safe (GRAS) status for use in beverages.
In a Bayesian network meta-analysis of 29 randomized trials of 12 medicinal herbs in adults with diagnosed or subthreshold anxiety, L-theanine did not beat placebo: the effect on the Hamilton Anxiety Scale was -0.49 points with a 95% credible interval of -6.54 to 5.57, which straddles zero in both directions. This is the only pooled quantitative estimate of L-theanine for anxiety found in the literature, and it is null.
Worth asking
The one pooled analysis of L-theanine for anxiety found it no better than placebo — if I'm spending money on it monthly, is there something with actual evidence I should try instead?
Source
Medicinal herbs for the treatment of anxiety: A systematic review and network meta-analysis. — Zhang W, Yan Y, Wu Y, et al. (2022)
Reputable peer-reviewed journal
Read the source: https://doi.org/10.1016/j.phrs.2022.106204
DOI: 10.1016/j.phrs.2022.106204
How this was scored
- Study design
- Meta-analysis of randomised trials
- Funding
- Independently funded
- Published in
- Reputable peer-reviewed journal
- Sample size
- not recorded
- Preregistered
- No
- Conflicts disclosed
- No
- Independent of proponent
- Yes
- Retracted
- No
Read the full scoring rubric, including what it can't tell you.
Published August 19, 2026.
Questions
How strong is the evidence behind this?
Resolv rates this source "strong evidence". Well-supported by good-quality research. It scores 80 out of 100 on our published rubric. One caveat travels with that badge: A null result across a wide credible interval means "not proven to work", not "proven not to work" — the L-theanine arm of this network rests on few small trials, so a modest real effect cannot be ruled out. The analysis came from a traditional Chinese medicine research institute, which if anything would bias it toward finding herbal benefits, making the null finding for L-theanine harder to dismiss. The score is calculated from recorded facts about the source — study design, funding, publication venue, sample size, preregistration — not typed in by an editor.
What is the source for this?
Medicinal herbs for the treatment of anxiety: A systematic review and network meta-analysis. — Zhang W, Yan Y, Wu Y, et al. (2022). Published in: Reputable peer-reviewed journal. DOI: 10.1016/j.phrs.2022.106204. The full source is linked on this page so you can read it yourself.
Who paid for this research, and does that matter?
Study design: Meta-analysis of randomised trials. Funding: Independently funded. The researchers were independent of whoever benefits from the result. Industry sponsorship is one of the most reliably measured biases in medicine, which is why funding carries real weight in the score rather than sitting in a footnote.
Is l-theanine, theanine, suntheanine, alphawave, gamma-glutamylethylamide, green tea amino acid FDA approved for this use?
No. Its current status is: Not FDA-evaluated for this use. L-theanine is sold in the US as a dietary supplement under the Dietary Supplement Health and Education Act of 1994 (DSHEA), and as a food additive it holds Generally Recognized as Safe (GRAS) status for use in beverages.
Is this medical advice?
This is information to bring to your prescriber, not medical advice and not a reason to change anything on your own. Nothing here is an instruction to stop or reduce a medication. If you are in crisis, call or text 988.
This is information to bring to your prescriber, not medical advice and not a reason to change anything on your own. Nothing here is an instruction to stop or reduce a medication. If you are in crisis, call or text 988.