Bright light exposure during acute tryptophan depletion prevents a lowering of mood in mildly seasonal women

Eur Neuropsychopharmacol. 2008 Jan;18(1):14-23. doi: 10.1016/j.euroneuro.2007.05.003. Epub 2007 Jun 19.


We investigated the influence of bright light exposure on the mood-lowering effect of acute tryptophan depletion (ATD). Mildly seasonal healthy young women without a personal or family history of psychiatric disorders remained in either dim or bright light during two test days. Tryptophan-deficient and nutritionally balanced amino acid mixtures were administered in counterbalanced order. Mood state was assessed using the Profile of Mood States (POMS) and Visual Analogue Scales (VAS). In dim light, ATD decreased POMS scores across most subscales, indicating a worsening of mood. In bright light, mood was unaffected by ATD. Thus, bright light blocked the worsening of mood caused by ATD. This was also observed on the positive mood VAS. These results indicate a direct, immediate interaction between bright light and serotonin function. Bright light might help protect against ATD-induced mood change by increasing serotonin above the threshold level below which there is a lowering of mood.

Publication types

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

MeSH terms

  • Adolescent
  • Adult
  • Affect / physiology*
  • Amino Acids / administration & dosage
  • Amino Acids / blood
  • Amino Acids / pharmacology
  • Cross-Over Studies
  • Double-Blind Method
  • Female
  • Humans
  • Light
  • Phototherapy*
  • Psychiatric Status Rating Scales
  • Seasonal Affective Disorder / metabolism
  • Seasonal Affective Disorder / therapy*
  • Seasons
  • Sleep / drug effects
  • Tryptophan / deficiency*


  • Amino Acids
  • Tryptophan