Also known as 5-Hydroxytryptophan, Griffonia simplicifolia
Direct metabolic precursor to serotonin, derived from Griffonia simplicifolia seeds, bypassing the rate-limiting step in serotonin synthesis; must not be combined with SSRIs, MAOIs, or other serotonergic drugs due to serotonin syndrome risk.
Reported side effects:Tolerability in RCT: 100 mg twice daily for 8 weeks in 166 patients produced no efficacy difference vs placebo; abstract reports no itemised adverse-event frequencies
Ask first if you take: antidepressants (SSRIs, SNRIs or MAOIs)
Suspect a side effect? Report it to the MHRA Yellow Card scheme ↗
We link to relevant studies and leave interpretation to you and your healthcare professional.
The large figures are what the studies reported for each thing they measured. Open a card for every result.
Colour keyReported a benefitNo clear benefitUnclearPossible harmAmber is for highlights, such as where the most research is. It never means a result was good.
Also measured alongside: Apathy symptoms (no clear benefit).
Every resultNo figure given: Obsession symptoms (reported a benefit); OCD symptoms (reported a benefit); Treatment response rate (reported a benefit).
Every resultWhat sources report about side effects, who should be careful, and medicines to ask about first.
| Reported effect | How often | Basis | Sources |
|---|---|---|---|
| Tolerability in RCT: 100 mg twice daily for 8 weeks in 166 patients produced no efficacy difference vs placebo; abstract reports no itemised adverse-event frequencies | unknown | Listed by PubMed corpus rows (PubMed 35940251) | Truyens M, et al. Effect of 5-Hydroxytryptophan on Fatigue in Quiescent Inflammatory Bowel Disease: A Randomized Controlled Trial. Gastroenterology 2022;163(5):1294-1305.e3 (PMID 35940251) |
| Reported effect | How often | Basis | Sources |
|---|---|---|---|
| Serotonin syndrome risk when 5-HTP (a direct serotonin precursor) is combined with serotonergic medicines — mechanism-level review evidence; mania was reported in a case after adding 5-HTP to an MAOI | unknown | Listed by PubMed corpus rows (PubMed 31075831, 21963353) | Francescangeli J, et al. The Serotonin Syndrome: From Molecular Mechanisms to Clinical Practice. Int J Mol Sci 2019;20(9):2288 (PMID 31075831)Pardo JV. Mania following addition of hydroxytryptophan to monoamine oxidase inhibitor. Gen Hosp Psychiatry 2012;34(1):102.e13-102.e14 (PMID 21963353)Das YT, Bagchi M, Bagchi D, Preuss HG. Safety of 5-hydroxy-L-tryptophan. Toxicol Lett 2004;150(1):111-122 (PMID 15068828) |
| Eosinophilia-myalgia-syndrome-like illness linked to historical impure batches: 'Peak X' family contaminants were found in all 8 commercial 5-HTP samples analysed (Klarskov 1999), while a later review concluded no definitive toxicity cases had emerged over 20 years of worldwide use and questioned the relevance of trace Peak X | unknown | Listed by PubMed corpus rows (PubMed 10721089, 15068828)sources differ — under review | Klarskov K, et al. Eosinophilia-myalgia syndrome case-associated contaminants in commercially available 5-hydroxytryptophan. Adv Exp Med Biol 1999;467:461-468 (PMID 10721089)Das YT, Bagchi M, Bagchi D, Preuss HG. Safety of 5-hydroxy-L-tryptophan. Toxicol Lett 2004;150(1):111-122 (PMID 15068828) |
| Severity | Medicine | Sources |
|---|---|---|
| ask first | antidepressants (SSRIs, SNRIs or MAOIs) — Combining 5-HTP with SSRIs/SNRIs/MAOIs stacks a serotonin precursor on reuptake blockade / MAO inhibition and raises serotonin syndrome risk (serotonin-syndrome review); mania occurred in a published case when 5-HTP was added to an MAOI. | Francescangeli J, et al. The Serotonin Syndrome: From Molecular Mechanisms to Clinical Practice. Int J Mol Sci 2019;20(9):2288 (PMID 31075831)Pardo JV. Mania following addition of hydroxytryptophan to monoamine oxidase inhibitor. Gen Hosp Psychiatry 2012;34(1):102.e13-102.e14 (PMID 21963353)Das YT, Bagchi M, Bagchi D, Preuss HG. Safety of 5-hydroxy-L-tryptophan. Toxicol Lett 2004;150(1):111-122 (PMID 15068828) |
Das YT, Bagchi M, Bagchi D, Preuss HG. Safety of 5-hydroxy-L-tryptophan. Toxicol Lett 2004;150(1):111-122 (PMID 15068828)Klarskov K, et al. Eosinophilia-myalgia syndrome case-associated contaminants in commercially available 5-hydroxytryptophan. Adv Exp Med Biol 1999;467:461-468 (PMID 10721089)Francescangeli J, et al. The Serotonin Syndrome: From Molecular Mechanisms to Clinical Practice. Int J Mol Sci 2019;20(9):2288 (PMID 31075831)Pardo JV. Mania following addition of hydroxytryptophan to monoamine oxidase inhibitor. Gen Hosp Psychiatry 2012;34(1):102.e13-102.e14 (PMID 21963353)Truyens M, et al. Effect of 5-Hydroxytryptophan on Fatigue in Quiescent Inflammatory Bowel Disease: A Randomized Controlled Trial. Gastroenterology 2022;163(5):1294-1305.e3 (PMID 35940251)
Audited published research for 5-HTP by condition. Drill into a pair page for the full breakdown.
What this means: Bars count reported findings, not treatment effectiveness or certainty.
One study may report several findings or appear in more than one pairing. Counts do not show the size of an effect. Comparable numerical estimates are not established for this summary.
| Compound and condition | Findings (count) | Studies (count) | Reported results (finding counts) | How sure? |
|---|---|---|---|---|
| Depression | 4 | 2 | Benefit: 3; no benefit: 1; harm: 0; unclear: 0; not recorded / unrecognised: 0 | Not formally graded |
| OCD | 5 | 1 | Benefit: 5; no benefit: 0; harm: 0; unclear: 0; not recorded / unrecognised: 0 | Not formally graded |
Where people report using it and what trials suggest
Common claims the trials do not support
Serotonin precursor with old, small depression trials and a genuinely important interaction risk with antidepressants.
Evidence grades reflect study quality and consistency, not marketing claims.
Ordered by strength of evidence, then result direction.
01Effects of 5-hydroxytryptophan on distinct types of depression: a systematic review and meta-analysisJavelle F, et al. · Nutrition reviews · 2020PMID 31504850 ↗02Symptomatic treatment of interferon-α-induced depression in hepatitis C: a systematic reviewBaraldi S, et al. · Journal of clinical psychopharmacology · 2012PMID 22722514 ↗03Tryptophan and 5-hydroxytryptophan for depressionShaw K, et al. · The Cochrane database of systematic reviews · 2002PMID 11869656 ↗04Are tryptophan and 5-hydroxytryptophan effective treatments for depression? A meta-analysisShaw K, et al. · The Australian and New Zealand journal of psychiatry · 2002PMID 12169147 ↗05Tryptophan and 5-hydroxytryptophan for depressionShaw K, et al. · The Cochrane database of systematic reviews · 2001PMID 11687048 ↗06The Impact of 5-Hydroxytryptophan Supplementation on Cognitive Function and Mood in Singapore Older Adults: A Randomized Controlled TrialLi S, et al. · Nutrients · 2025PMID 40944161 ↗Reported results grouped by condition. Values and units are preserved as recorded; missing information is not estimated.
How to read this table
Reported direction, numerical results and study design are separate. Certainty has not been formally graded in this table.
| What was measured | Reported findings | Result and units | Reported sample and duration | Study / source |
|---|---|---|---|---|
| depression remission rate | Depression remission rate was 0.65 across 13 studies, though placebo comparisons were limited. (95% confidence interval [CI], 0.55-0.78)Benefit seen | 0.65 Recorded unit: Not reported | Sample (as reported): 13 Follow-up: Not reported | Meta-analysis · 2020 Study detailsEffects of 5-hydroxytryptophan on distinct types of depression: a systematic review and meta-analysis. Meta-Analysis |
| Hedges' g for depression symptoms | Depression scores showed a large effect size of 1.11 in 7 studies, with limited placebo controls. (95%CI, 0.53-1.69)Benefit seen | 1.11 Recorded unit: Not reported | Sample (as reported): 7 Follow-up: Not reported | Meta-analysis · 2020 Study detailsEffects of 5-hydroxytryptophan on distinct types of depression: a systematic review and meta-analysis. Meta-Analysis |
| Apathy symptoms (AS) | No effect on apathy symptoms was seen with 5-HTP vs placebo in 25 people over 4 weeks.No clear benefit | Not reported Recorded unit: Not reported | Sample (as reported): 25 Follow-up: 4 weeks | Randomised trial · 2020 Study detailsEfficacy and safety of 5-hydroxytryptophan on depression and apathy in Parkinson's disease: a preliminary finding. Randomized Controlled Trial |
| Depressive symptoms (HDRS) | Depression scores improved significantly with 5-HTP vs placebo in 25 people over 4 weeks.Benefit seen | Not reported Recorded unit: Not reported | Sample (as reported): 25 Follow-up: 4 weeks | Randomised trial · 2020 Study detailsEfficacy and safety of 5-hydroxytryptophan on depression and apathy in Parkinson's disease: a preliminary finding. Randomized Controlled Trial |
| What was measured | Reported findings | Result and units | Reported sample and duration | Study / source |
|---|---|---|---|---|
| Complete treatment response rate | 5-hydroxytryptophan improved Complete treatment response rate (P = 0.001) compared with placebo in 60 (12-week). (P = 0.001)Benefit seen | Not reported Recorded unit: Not reported | Sample (as reported): 60 Follow-up: 12-week | Randomised trial · 2020 Study details5-Hydroxytryptophan as adjuvant therapy in treatment of moderate to severe obsessive-compulsive disorder: a double-blind randomized trial with placebo control. Randomized Controlled Trial |
| Compulsion subscale score | 5-hydroxytryptophan improved Compulsion subscale score (F = 6.64; df = 2.01; P-value = 0.002) compared with placebo in 60 (12-week).Benefit seen | F = 6.64 Recorded unit: Not reported | Sample (as reported): 60 Follow-up: 12-week | Randomised trial · 2020 Study details5-Hydroxytryptophan as adjuvant therapy in treatment of moderate to severe obsessive-compulsive disorder: a double-blind randomized trial with placebo control. Randomized Controlled Trial |
| Obsession subscale score | 5-hydroxytryptophan improved Obsession subscale score (F = 8.25; df = 1.91; P-value = 0.001) compared with placebo in 60 (12-week).Benefit seen | F = 8.25 Recorded unit: Not reported | Sample (as reported): 60 Follow-up: 12-week | Randomised trial · 2020 Study details5-Hydroxytryptophan as adjuvant therapy in treatment of moderate to severe obsessive-compulsive disorder: a double-blind randomized trial with placebo control. Randomized Controlled Trial |
| Partial treatment response rate | 5-hydroxytryptophan improved Partial treatment response rate (P = 0.032) compared with placebo in 60 (12-week). (P = 0.032)Benefit seen | Not reported Recorded unit: Not reported | Sample (as reported): 60 Follow-up: 12-week | Randomised trial · 2020 Study details5-Hydroxytryptophan as adjuvant therapy in treatment of moderate to severe obsessive-compulsive disorder: a double-blind randomized trial with placebo control. Randomized Controlled Trial |
| Total Y-BOCS score | 5-hydroxytryptophan improved Total Y-BOCS score (F = 12.07; df = 2.29; P-value <0.001) compared with placebo in 60 (12-week).Benefit seen | F = 12.07 Recorded unit: Not reported | Sample (as reported): 60 Follow-up: 12-week | Randomised trial · 2020 Study details5-Hydroxytryptophan as adjuvant therapy in treatment of moderate to severe obsessive-compulsive disorder: a double-blind randomized trial with placebo control. Randomized Controlled Trial |
Associated conditions and community-reported outcomes, wrapped together on one page. Aggregates appear only once enough reports arrive.
How this compound is sold in the UK, and where our readers typically find it.
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