Winter Depression: Integrating Mood, Circadian Rhythms, and the Sleep/Wake and Light/Dark Cycles into a Bio-Psycho-Social-Environmental Model

Alfred J. Lewy, Jonathan S. Emens, Jeannie B. Songer, Neelam Sims, Amber L. Laurie, Steven C. Fiala, Allie Buti

Research output: Contribution to journalReview article

35 Scopus citations


The phase-shift hypothesis (PSH) states that most patients who have seasonal affective disorder become depressed in the winter because of a delay in circadian rhythms with respect to the sleep/wake cycle. According to the PSH, these patients should respond preferentially to the antidepressant effects of bright light exposure when it is scheduled in the morning to provide a corrective phase advance and restore optimum alignment between the circadian rhythms tightly coupled to the endogenous circadian pacemaker and the rhythms that are related to the sleep/wake cycle. Recent support for the PSH has come from studies in which symptom severity was shown to correlate with the degree of circadian misalignment. This article includes a review of resolved and unresolved issues related to circadian rhythms.

Original languageEnglish (US)
Pages (from-to)285-299
Number of pages15
JournalSleep Medicine Clinics
Issue number2
StatePublished - Jun 1 2009



  • Bio-psycho-social-environmental model
  • Dim light melatonin onset (DLMO)
  • Light
  • Melatonin
  • Phase-angle difference (PAD)
  • Winter depression (SAD)

ASJC Scopus subject areas

  • Neuropsychology and Physiological Psychology
  • Clinical Psychology
  • Clinical Neurology
  • Psychiatry and Mental health

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