5-HTP
Research reviewed: Up until 03/2026
5-HTP (5-Hydroxytryptophan) is a dietary supplement with 8 published peer-reviewed studies involving 896 participants, researched for Depression & Mood, Sleep Quality, Fibromyalgia & Chronic Pain and 1 more areas.
Evidence at a Glance
Strength is scored by study design, sample size, study type, and outcomes
Depression & Mood
ModerateSleep Quality
ModerateFibromyalgia & Chronic Pain
ModerateAnxiety & Stress
ModerateResearch Visualised
Visual breakdown of the clinical data.
Study Quality Breakdown
What types of studies were conducted
Participants Per Study
Larger samples = more reliable results
Research Timeline
When the studies were published
All Studies
Detailed breakdown of each trial. Click to expand.
Depression & Mood
To compare the efficacy of 5-HTP with a placebo in treating depression.
Study Type
Double-blind, placebo-controlled
Purpose
To compare the efficacy of 5-HTP with a placebo in treating depression.
Dose
200 mg/day 5-HTP
Participants
63 patients with a diagnosis of depression
Duration
4 weeks
Results
5-HTP produced significantly greater reduction in HAM-D scores compared to placebo. More than 50% of 5-HTP-treated patients showed clinically meaningful improvement vs placebo group.
How They Measured It
Hamilton Depression Rating Scale (HAM-D)
To compare l-5-hydroxytryptophan (5-HTP) with fluoxetine in patients with first depressive episode.
Study Type
Randomised, double-blind, controlled
Purpose
To compare l-5-hydroxytryptophan (5-HTP) with fluoxetine in patients with first depressive episode.
Dose
100 mg/day 5-HTP vs 20 mg/day fluoxetine
Participants
40 patients with first depressive episode
Duration
8 weeks
Results
Both 5-HTP and fluoxetine produced comparable reductions in HAM-D scores by week 8. 5-HTP showed similar efficacy to fluoxetine with a good tolerability profile.
How They Measured It
Hamilton Rating Scale for Depression (HAM-D), Clinical Global Impression (CGI)
To evaluate the effects of 5-hydroxytryptophan on distinct types of depression.
Study Type
Systematic review and meta-analysis
Purpose
To evaluate the effects of 5-hydroxytryptophan on distinct types of depression.
Dose
50-600 mg/day 5-HTP
Participants
Meta-analysis of placebo-controlled trials
Duration
Various
Results
5-HTP showed beneficial effects on depression symptoms in placebo-controlled trials, particularly in mild-to-moderate depression. Methodological limitations were noted in older studies. Larger well-designed RCTs needed.
How They Measured It
HAM-D, MADRS, IDS-SR across included RCTs
Sleep Quality
To assess the impact of 5-HTP supplementation on sleep quality and gut microbiota composition in older adults.
Study Type
Randomised, single-blind, placebo-controlled
Purpose
To assess the impact of 5-HTP supplementation on sleep quality and gut microbiota composition in older adults.
Dose
100 mg/day 5-HTP
Participants
40 older adults with sleep complaints
Duration
8 weeks
Results
5-HTP supplementation significantly improved overall sleep quality scores (PSQI) compared to placebo. Improvements in sleep latency and subjective sleep quality were observed. Gut microbiota diversity also improved.
How They Measured It
Pittsburgh Sleep Quality Index (PSQI), polysomnography, gut microbiota analysis
To investigate the impact of 5-HTP supplementation on cognitive function and mood in older Singaporean adults.
Study Type
Randomised, single-blind, placebo-controlled
Purpose
To investigate the impact of 5-HTP supplementation on cognitive function and mood in older Singaporean adults.
Dose
100 mg/day 5-HTP capsules taken 20-30 minutes before bedtime
Participants
60 older adults in Singapore aged 60 years and over
Duration
12 weeks
Results
5-HTP significantly improved global cognitive function, mood, and sleep quality compared to control. Significant improvements in MoCA scores, depression, anxiety, and stress subscales of DASS-21 were observed.
How They Measured It
MoCA, DASS-21, Pittsburgh Sleep Quality Index, physical function tests
Fibromyalgia & Chronic Pain
To evaluate the effects of 5-HTP on symptoms of primary fibromyalgia syndrome including pain, sleep, fatigue, and anxiety.
Study Type
Open-label clinical study
Purpose
To evaluate the effects of 5-HTP on symptoms of primary fibromyalgia syndrome including pain, sleep, fatigue, and anxiety.
Dose
100 mg three times daily (300 mg/day) of 5-HTP
Participants
50 patients with primary fibromyalgia
Duration
90 days
Results
All clinical variables (number of tender points, anxiety, pain intensity, quality of sleep, fatigue) showed significant improvement (P<0.001). 5-HTP was well tolerated with no serious adverse effects.
How They Measured It
Tender point count, VAS pain score, Hamilton Anxiety Scale, sleep quality assessment, fatigue rating
To evaluate 5-HTP vs placebo in the treatment of primary fibromyalgia syndrome.
Study Type
Randomised, double-blind, placebo-controlled
Purpose
To evaluate 5-HTP vs placebo in the treatment of primary fibromyalgia syndrome.
Dose
100 mg three times daily (300 mg/day) of 5-HTP
Participants
50 patients with fibromyalgia
Duration
30 days
Results
All clinical parameters were significantly improved by treatment with 5-HTP compared to placebo. Only mild and transient side effects (mainly gastrointestinal) were noted in the 5-HTP group.
How They Measured It
Tender point count, VAS pain, anxiety, fatigue, sleep quality
Anxiety & Stress
To review the evidence for tryptophan and 5-HTP in treating depression and anxiety disorders.
Study Type
Systematic review
Purpose
To review the evidence for tryptophan and 5-HTP in treating depression and anxiety disorders.
Dose
Various (50-600 mg/day)
Participants
Systematic review of available clinical trials
Duration
Various
Results
Evidence supports modest but significant anxiolytic and antidepressant effects of 5-HTP. 5-HTP and L-tryptophan are more effective than placebo for depression, with evidence for anxiety reduction also identified.
How They Measured It
Anxiety measures, depression scales across included RCTs
Frequently Asked Questions
Common questions about 5-HTP research
There are currently 12 peer-reviewed studies on 5-HTP (5-Hydroxytryptophan), involving 896 total participants. Research covers Depression & mood, Sleep quality, Anxiety and 1 more areas. The overall evidence strength is rated as Very Strong.
The evidence is currently rated as "Very Strong Evidence". This rating is based on study design quality (randomisation, blinding, placebo controls), sample sizes, study types (8 human studies), and reported outcomes.
5-HTP has been researched for: Depression & mood, Sleep quality, Anxiety, Fibromyalgia & pain. Each area has its own body of evidence which you can explore in the study breakdowns above.
Yes, 8 out of 12 studies are human trials. Human trials carry more weight in our evidence scoring system.
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