Tryptophan depletion causes a rapid lowering of mood in normal males.
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.
D000293:Adolescent; D000328:Adult; D000596:Amino Acids / Q000494:pharmacology; D001288:Attention / Q000187:drug effects; D003863:Depression / Q000139:chemically induced; D004644:Emotions / Q000187:drug effects*; D006801:Humans; D008297:Male; D012701:Serotonin / Q000502:physiology; D014364:Tryptophan / Q000097:blood / Q000494:pharmacology*
D000596:Amino Acids; D012701:Serotonin; D014364:Tryptophan