Tryptophan depletion causes a rapid lowering of mood in normal males

Psychopharmacology (Berl). 1985;87(2):173-7. doi: 10.1007/BF00431803.


Normal male human subjects ingested amino acid mixtures which were tryptophan-free, balanced or contained excess tryptophan. The tryptophan-free mixture causes a marked depletion of plasma tryptophan by 5 h. At this time the subjects in the tryptophan-free group had significantly elevated scores on the depression scale of the Multiple Affect Adjective Checklist. The tryptophan-free group also performed worse than the other two groups in a proofreading task carried out while listening to a tape with themes of hopelessness and helplessness (dysphoric distractor). Cognitive theories of depression predict greater distractability of depressed individuals by dysphoric themes. Thus, both measures indicate a rapid mood lowering effect of tryptophan depletion in normal males. This effect is probably mediated by a lowering of brain 5-hydroxytryptamine. Although the mood-lowering effect was not as great as that seen in depressed patients, our results suggest that low brain 5HT might be one factor precipitating depression in some patients.

Publication types

  • Clinical Trial
  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Amino Acids / pharmacology
  • Attention / drug effects
  • Depression / chemically induced
  • Emotions / drug effects*
  • Humans
  • Male
  • Serotonin / physiology
  • Tryptophan / blood
  • Tryptophan / pharmacology*


  • Amino Acids
  • Serotonin
  • Tryptophan