Effects of tryptophan depletion vs catecholamine depletion in patients with seasonal affective disorder in remission with light therapy

Alexander Neumeister, Erick H. Turner, Jefferey R. Matthews, Teodor T. Postolache, Ronald L. Barnett, Manfred Rauh, Rina G. Vetticad, Siegfried Kasper, Norman E. Rosenthal

Research output: Contribution to journalArticlepeer-review

130 Scopus citations


Background: Although hypotheses about the therapeutic mechanism of action of light therapy have focused on serotonergic mechanisms, the potential role, if any, of catecholaminergic pathways has not been fully explored. Methods: Sixteen patients with seasonal affective disorder who had responded to a standard regimen of daily 10000-lux light therapy were enrolled in a doubleblind, placebo-controlled, randomized crossover study. We compared the effects of tryptophan depletion with catecholamine depletion and sham depletion. Ingestion of a tryptophan-free amino acid beverage plus amino acid capsules was used to deplete tryptophan. Administration of the tyrosine hydroxylase inhibitor α-methyl-paratyrosine was used to deplete catecholamines. Diphenhydramine hydrochloride was used as an active placebo during sham depletion. The effects of these interventions were evaluated with measures of depression, plasma tryptophan levels, and plasma catecholamine metabolites. Results: Tryptophan depletion significantly decreased plasma total and free tryptophan levels. Catecholamine depletion significantly decreased plasma 3-methoxy-4- hydroxyphenylethyleneglycol and homovanillic acid levels. Both tryptophan depletion and catecholamine depletion, compared with sham depletion, induced a robust increase (P<.001, repeated-measures analysis of variance) in depressive symptoms as measured with the Hamilton Depression Rating Scale, Seasonal Affective Disorder Version. Conclusions: The beneficial effects of light therapy in the treatment of seasonal affective disorder are reversed by both tryptophan depletion and catecholamine depletion. These findings confirm previous work showing that serotonin plays an important role in the mechanism of action of light therapy and provide new evidence that brain catecholaminergic systems may also be involved.

Original languageEnglish (US)
Pages (from-to)524-530
Number of pages7
JournalArchives of General Psychiatry
Issue number6
StatePublished - 1998

ASJC Scopus subject areas

  • Arts and Humanities (miscellaneous)
  • Psychiatry and Mental health


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