Skip to the main content
Open WellbeingWhat the studies actually measured

Mood, stress and thinking

5-HTPand Depression

Both sources here measured lower depression.

How sure anyone can be

Low certainty, level 2 of 4

Further research is likely to change this.

The most certain of the two findings here; each record carries its own.

The numbers reported

One source’s range, drawn against its own line of no difference and scaled to its own numbers.

1.34.1 odds ratio13.2

This range stays on one side of the no-difference line.

Bar the confidence interval — the range the true effect is likely to sit inNotch the number the source reportedLine where there would be no difference at all

Two sources, newest first

What we read is the published abstract, not the full paper, so a blank below may still be printed in the paper itself. A fixed rule worked this out from the source’s own fields. Nobody checked this rating by hand.

  • Systematic review, 2020

    Low certainty, level 2 of 4

    Effects of 5-hydroxytryptophan on distinct types of depression: a systematic review and meta-analysis.

    Nutr Rev. 2020;78(1):77-88. doi:10.1093/nutrit/nuz039. PMID:31504850.

    Number reported
    1.11 standardised effect size
    Which way it went
    Lower
    Likely range
    0.53 to 1.69
    Source’s own words
    Hedges' g on depression questionnaires; positive is the reported large questionnaire change confirming a reduction in depression
    Who was studied
    Depressed patients
    Compared with
    mixed experimental designs (few include placebo groups)
    Amount taken
    Not in the abstract
    For how long
    Not in the abstract
    Disagreement between studies
    I2 = 76%, τ2 = 0.379
    Kind of record
    Journal article
    How this rating was reachedstarts at High, 2 steps down: imprecision and inconsistency
    1. Starts at High
    2. Imprecision brought it down to Moderatethe abstract does not state how many participants were pooledNot in the abstract
    3. Inconsistency brought it down to Lowheterogeneity across pooled studies is high (I² = 76%)Reported in the abstract
    4. Ends at Low2 steps down.
    Checked, nothing to step it down for
    risk of bias and indirectness

    Imprecision stops at the first check that applies; others may apply too.

    Source saved; quote checked byte-for-byte against it by software; no signature.

    Read the abstract on PubMed

  • Systematic review, 2002 · 2 studies pooled · 64 participants

    Low certainty, level 2 of 4

    Are tryptophan and 5-hydroxytryptophan effective treatments for depression? A meta-analysis.

    Aust N Z J Psychiatry. 2002;36(4):488-91. doi:10.1046/j.1440-1614.2002.01046.x. PMID:12169147.

    Number reported
    4.1 odds ratio
    Which way it went
    Lower
    Likely range
    1.3 to 13.2
    Source’s own words
    Peto odds ratio for improvement in depression, 5-HTP or L-tryptophan vs placebo
    Who was studied
    Adult with unipolar depression
    Compared with
    placebo
    Amount taken
    Not in the abstract
    For how long
    Not in the abstract
    Disagreement between studies
    Not in the abstract
    Kind of record
    Journal article
    How this rating was reachedstarts at High, 2 steps down: risk of bias and imprecision
    1. Starts at High
    2. Risk of bias brought it down to Moderatethe abstract reports no risk-of-bias or quality appraisal, so study limitations cannot be ruled outNot in the abstract
    3. Imprecision brought it down to Low64 participants is below the 400-participant optimal information size floorReported in the abstract
    4. Ends at Low2 steps down.
    Checked, nothing to step it down for
    indirectness
    Inconsistency
    No high disagreement reported between the 2 studies it pooled

    Imprecision stops at the first check that applies; others may apply too.

    AI-reviewed & signed — an AI agent re-read this finding against the saved source and checked that the quote, the numbers, the units and the direction match it. No person read it. The owner authorised the agent to sign the batch with the owner's key, and every build rechecks that signature against these exact bytes.

    Read the abstract on PubMed

What is still missing from these readings

  • One do not say how many people took part.
  • Amount taken — Not in the abstract.
  • For how long — Not in the abstract.

Something nobody wrote down is never a zero and never a guess.

Still to read for 5-HTP

Five of the 15 things on our list for 5-HTP have no reading here yet:

  • Cognitive performance
  • Migraine frequency
  • Migraine intensity
  • Salivary cortisol
  • Sleep quality (subjective)

Still to read means nobody here has got to it, not that it was tried and did nothing or that no research exists. A pairing on no list is not a gap: we never set out to read it.

Read next

This is a library, not advice. No recommendation, no dose, no diagnosis, no ranking. We never ask about your symptoms, and nothing here is tailored to you.