Evidence tier
Preliminary
Research weight
Citations
15 verified / 15
Classification
Sleep & Mood
❝
What the evidence says. Early or small human trials; promising but not yet conclusive.
What is 5-HTP?
5-HTP is a sleep and mood supplement used for mood support. NutriDex grades the human evidence as Preliminary. 5-HTP is the direct precursor to serotonin and crosses the blood-brain barrier. Small early trials suggested antidepressant and appetite-suppressing effects, but the evidence base is thin and dated, and study quality is poor. Its biggest concern is interaction risk: combined with SSRIs/MAOIs it can cause dangerous serotonin syndrome. Use only with medical guidance.
Purported Benefits
✓Mood support
✓Appetite/satiety
✓Possible sleep aid
Evidence by outcome
The same supplement can be well-proven for one use and unproven for another — here is the human evidence graded outcome by outcome.
| Outcome | Evidence | Effect | Studies |
|---|---|---|---|
| Depression / moodCochrane found only 2 quality trials; a 2020 MA reported large effect but flagged poor methodology — evidence thin and dated. | Mixed | ↑ benefit | 3 |
| Appetite / weight lossSingle small 1992 RCT showed reduced appetite and weight loss; not replicated. | Preliminary | ↑ benefit · moderate | 1 |
| Sleep qualityOne 12-wk single-blind RCT in 30 older adults found modest gains in select sleep components, mainly in poor sleepers. | Preliminary | ↑ benefit · small | 1 |
| Fatigue (IBD)Multicenter crossover RCT (166 pts) found no fatigue benefit over placebo despite raising serum serotonin. | Moderate | — no effect · negligible | 1 |
| Serotonin syndrome risk (with SSRIs/MAOIs)Authoritative monograph warns of serotonin syndrome with SSRIs/MAOIs/linezolid; mechanistically established interaction risk. | Moderate | ⚠ risk | 1 |
Dosing & Compounds
Typical Dose
50–300 mg/day; start low. Do NOT combine with antidepressants.
Active Compounds
Safety & Cautions
GI upset common. Serious serotonin-syndrome risk with serotonergic drugs. Historic EMS concern from contamination. Educational only — always check with your doctor or pharmacist before combining 5-HTP with any medicine.
5-HTP drug interactions
Known or theoretical interactions between 5-HTP and common medications — educational, not exhaustive. Always check with your doctor or pharmacist before combining 5-HTP with any medicine.
Avoid
SSRIs / SNRIs / MAOIs
Can cause serotonin syndrome: agitation, confusion, rapid heart rate, high temperature.
5-HTP is the direct precursor to serotonin; with serotonergic drugs it drives excess serotonin. MedlinePlus — Serotonin syndrome
Key Studies ★ 15 studies
meta-analysis
Javelle 2020 meta-analysis
✓ PubMed
Systematic review/meta-analysis (13 studies; 7 pooled) found 5-HTP better than placebo for depression, with a remission rate of 0.65 (95% CI 0.55-0.78) and large effect (Hedges g 1.11), but flagged methodological limitations.
Cochrane review
Shaw 2002 (Cochrane)
✓ PubMed
Limited evidence of antidepressant effect; quality too low to be sure.
Systematic review
Shaw, Turner & Del Mar 2002 (Cochrane Review)
✓ PubMed
Cochrane review of tryptophan and 5-HTP for depression. Of 108 trials, only 2 (64 patients) met quality criteria. These favored 5-HTP/tryptophan over placebo for alleviating depression (Peto OR 4.10, 95% CI 1.28-13.15; NNT 2.78), but evidence judged insufficient quality to be conclusive; clinical usefulness deemed limited given proven safe alternatives and unresolved eosinophilia-myalgia syndrome concern.
RCT
Rahman 2024 (sleep RCT)
✓ PubMed
In a 12-week single-blind RCT of 30 older adults (~66 y), 100 mg/day 5-HTP modestly improved selected sleep-quality components and gut microbiota composition, most notably in poor sleepers.
RCT
Singapore cognition/mood RCT 2025
✓ Full text
In a 12-week single-blind RCT of 30 Singaporean older adults (~66 y), 100 mg/day 5-HTP did not significantly improve cognitive function or mood versus control.
RCT
Li et al. 2025 (Nutrients)
✓ PubMed
12-week single-blind RCT, 30 Singaporean older adults (66±3 y), 100 mg/day 5-HTP vs control. 5-HTP group significantly improved global cognition (MoCA 26.6 to 27.6, p<0.05), raised serum serotonin, and reduced depression scores (GDS 1.2 to 0.7, p<0.05). No effect on anxiety (GAI) or amyloid-beta/GABA biomarkers. Preliminary; small sample and short duration.
RCT
Steenbergen 2021 (social cognition RCT)
✓ PubMed
In a randomized controlled trial, acute 5-HTP supplementation (vs tryptophan-enriched diet and placebo) altered social cognition at neural and behavioral levels in healthy adults.
rct
Cossey 2022 (IBD fatigue RCT, Gastroenterology)
✓ PubMed
In a multicenter crossover RCT of 166 patients with quiescent IBD and fatigue, 100 mg 5-HTP twice daily did not reduce fatigue better than placebo (>=20% fVAS reduction: 35.6% vs 37.6%) despite raising serum serotonin.
Safety / toxicology
Hinz, Stein & Cole 2021 (5-HTP toxicology review)
✓ Full text
Comprehensive review of 5-HTP biosynthesis, physiology and toxicology summarizing the eosinophilia-myalgia syndrome (EMS) signal and contaminant 'peak X' concerns relevant to supplement safety.
Clinical trial
Cangiano 1992
✓ PubMed
Reduced appetite and promoted weight loss in a small trial.
rct
Caruso 1990 (fibromyalgia RCT)
✓ PubMed
In a 30-day double-blind RCT of 50 primary fibromyalgia patients, 100 mg 5-HTP three times daily significantly improved tender points, pain, morning stiffness, sleep, and anxiety versus placebo, with only mild transient side effects.
RCT
5-HTP + creatine pilot (treatment-resistant MDD), Kious et al.
✓ PubMed
Open-label pilot in 15 women with SSRI/SNRI-resistant major depression: adjunctive 5-HTP plus creatine reduced mean HAM-D from 18.6 to 7.5 at week 8 with 67% achieving >=50% response; well tolerated.
lab
Klarskov 1999 (Peak X contaminants in 5-HTP)
✓ PubMed
HPLC-MS analysis found that all 8 commercially available 5-HTP samples contained three or more 'peak X' family contaminants (MW 234 Da) of the type associated with eosinophilia-myalgia syndrome.
institutional
Memorial Sloan Kettering Cancer Center (5-HTP monograph)
✓ Source
Authoritative integrative-medicine review warns that 5-HTP can precipitate serotonin syndrome when combined with SSRIs/MAOIs/linezolid, can cause a scleroderma-like illness with carbidopa, and may produce false 5-HIAA urine test results.
Mechanism
Birdsall 1998 review
✓ PubMed
Plausible serotonergic effects but inadequate large trials.