Effects of 5-hydroxytryptophan on distinct types of depression: a systematic review and meta-analysis.
Most of the 5-HTP studies had no placebo group, so people got better but nobody knows against what — does that change how much weight we should put on the numbers?
Reasonable evidence with real limitations. how we score evidence
Caveat on this rating: A pooled remission rate from mostly uncontrolled trials measures how many people improved, not how many improved because of 5-HTP; depression remits substantially on placebo and with time. Classified here as a systematic review of largely non-randomised evidence rather than a meta-analysis of RCTs for exactly that reason.
5-HTP is sold in the US as a dietary supplement under DSHEA. It has never been approved by the FDA to treat depression, anxiety, insomnia, fibromyalgia, or anything else, and no FDA review of safety, purity, or effectiveness precedes it going on sale.
Thirteen studies entered the systematic review and seven the meta-analysis, yielding a pooled depression remission rate of 0.65 (95% CI 0.55 to 0.78) and a large effect on questionnaire scores (Hedges' g 1.11, 95% CI 0.53 to 1.69) with substantial heterogeneity (I-squared 76%). The authors' own risk-of-bias assessment rated the underlying studies as relatively weak, noting that few included placebo groups — which is why a 65% remission rate here is not comparable to a placebo-controlled remission rate, and why they call for placebo-controlled trials in well-defined patients.
Worth asking
Most of the 5-HTP studies had no placebo group, so people got better but nobody knows against what — does that change how much weight we should put on the numbers?
Source
Effects of 5-hydroxytryptophan on distinct types of depression: a systematic review and meta-analysis. — Javelle F, Lampit A, Bloch W, Häussermann P, Johnson SL, Zimmer P. (2020)
Reputable peer-reviewed journal
Read the source: https://doi.org/10.1093/nutrit/nuz039
DOI: 10.1093/nutrit/nuz039
How this was scored
- Study design
- Systematic review of observational studies
- Funding
- Funding not disclosed
- Published in
- Reputable peer-reviewed journal
- Sample size
- not recorded
- Preregistered
- Yes
- 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 "moderate evidence". Reasonable evidence with real limitations. It scores 63 out of 100 on our published rubric. One caveat travels with that badge: A pooled remission rate from mostly uncontrolled trials measures how many people improved, not how many improved because of 5-HTP; depression remits substantially on placebo and with time. Classified here as a systematic review of largely non-randomised evidence rather than a meta-analysis of RCTs for exactly that reason. 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?
Effects of 5-hydroxytryptophan on distinct types of depression: a systematic review and meta-analysis. — Javelle F, Lampit A, Bloch W, Häussermann P, Johnson SL, Zimmer P. (2020). Published in: Reputable peer-reviewed journal. DOI: 10.1093/nutrit/nuz039. 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: Systematic review of observational studies. Funding: Funding not disclosed. 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 5-htp, 5-hydroxytryptophan, l-5-htp, oxitriptan, griffonia simplicifolia extract FDA approved for this use?
No. Its current status is: Not FDA-evaluated for this use. 5-HTP is sold in the US as a dietary supplement under DSHEA. It has never been approved by the FDA to treat depression, anxiety, insomnia, fibromyalgia, or anything else, and no FDA review of safety, purity, or effectiveness precedes it going on sale.
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.