Evidence Trace, complete trial record

In plain terms

In plain terms: 5-HTP (5-Hydroxytryptophan) shows early signals in human research but the evidence is limited -- small trials, surrogate endpoints, or not yet independently replicated. It is an emerging area, not yet a proven one.

5-HTP (5-Hydroxytryptophan)

C Limited: small, mixed or unreplicated trials

Category Supplements

Evidence Small randomized trials and two pooled analyses, low quality; one large null trial on fatigue

Reviewed July 2026

PMIDs 35940251 · 11869656 · 31504850 · 23380314 · 32067288 · 42160304

The endpoint this grade is based on: self_report, Depressive symptoms, on small older trials of low quality; the one large modern trial, in fatigue, was null

The evidence as the record states it

Evidence record

PMID 35940251 PMID 11869656 PMID 31504850 PMID 23380314 PMID 32067288 PMID 42160304

Depressive symptoms: Shaw et al. (Cochrane, 2002; PMID 11869656) found only 2 of 108 trials (64 patients) good enough to pool and called the positive result inconclusive; Javelle et al. (Nutr Rev, 2020; PMID 31504850) pooled 7 mostly uncontrolled studies and rated them weak; Jangid et al. (2013; PMID 23380314) and Meloni et al. (2020; PMID 32067288) are small trials, one without placebo. Fatigue: Truyens et al. (Gastroenterology, 2022; PMID 35940251), the largest and best 5-HTP trial, 166 patients with inactive inflammatory bowel disease, was null on its primary endpoint and every secondary one. Safety: the Cochrane review states the possible association with eosinophilia-myalgia syndrome has not been resolved; Jackson et al. (PLoS One, 2026; PMID 42160304) report fatigue, nausea or vomiting in 19.6 percent of adults after a single dose; serotonergic drug interactions are listed under drug conflicts. Grade C rests on the depressive-symptom trials and their low quality; the fatigue use is D, Route 2.

PMID 35940251 PMID 11869656 PMID 31504850 PMID 23380314 PMID 32067288 PMID 42160304

Evidence by specific use

Depressive symptoms

Grade C

Shaw et al. (Cochrane, 2002; PMID 11869656): of 108 trials located, only 2 (64 patients) were of sufficient quality; pooled, 5-HTP and tryptophan beat placebo (Peto OR 4.10, 95% CI 1.28 to 13.15) but the authors call the evidence insufficient to be conclusive. Javelle et al. (Nutr Rev, 2020; PMID 31504850): 13 studies, 7 pooled, remission rate 0.65, large effect, high heterogeneity, and the authors rate the studies weak with few placebo groups. Jangid et al. (Asian J Psychiatr, 2013; PMID 23380314): 60 patients, 5-HTP matched fluoxetine on HAM-D over 8 weeks, no placebo arm. Meloni et al. (Eur J Neurol, 2020; PMID 32067288): 25 people with Parkinson's disease, crossover, HDRS improved on 50 mg/day. Small trials, mostly old, low quality: C.

PMID 11869656 PMID 31504850 PMID 23380314 PMID 32067288

Fatigue in quiescent inflammatory bowel disease

Grade D

PMID 35940251

Why Grade C and not Grade B

Grade C reflects early or limited human evidence -- small trials, surrogate endpoints, or preliminary findings not yet independently replicated. The evidence points in a promising direction but does not yet meet the standard for Grade B. A single well-powered, independently replicated trial with a meaningful endpoint would move this to Grade B or higher.

What would move this grade

A well-powered randomized trial with an objective, clinically meaningful primary endpoint and at least one independent replication would support Grade B or higher.

How to track whether this is working The PHQ-9 or HAMD-17 at baseline and 6 weeks for depression applications. Sleep quality with the PSQI at baseline and 4 weeks for sleep applications. Combining 5-HTP with SSRIs, MAOIs or triptans carries a documented risk of serotonin syndrome and belongs under physician supervision.