Seasonal affective disorder and season-dependent abnormalities of melatonin suppression by light

Lancet. 1990 Sep 22;336(8717):703-6. doi: 10.1016/0140-6736(90)92202-s.


Twelve patients with seasonal affective disorder (SAD) and eleven normal controls were exposed to 2000 lux and 300 lux of artificial full-spectrum light on consecutive nights during the winter. Suppression of melatonin secretion under the two light intensities was measured and the difference between their effects was taken as a measure of light sensitivity. The test was repeated in summer in both groups, when the SAD subjects were well. The SAD but not the normal group showed a significant seasonal variation in sensitivity to light. There was evidence of supersensitivity in the winter but also of subsensitivity to light in the summer.

Publication types

  • Clinical Trial
  • Comparative Study
  • Randomized Controlled Trial

MeSH terms

  • Adult
  • Evaluation Studies as Topic
  • Female
  • Humans
  • Light / adverse effects*
  • Male
  • Melatonin / blood
  • Melatonin / metabolism*
  • Middle Aged
  • Mood Disorders / blood
  • Mood Disorders / etiology
  • Mood Disorders / therapy*
  • Periodicity*
  • Phototherapy*
  • Randomized Controlled Trials as Topic
  • Seasons*
  • Suprachiasmatic Nucleus / metabolism
  • Time Factors


  • Melatonin