Abstract
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 language | English (US) |
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Pages (from-to) | 285-299 |
Number of pages | 15 |
Journal | Sleep Medicine Clinics |
Volume | 4 |
Issue number | 2 |
DOIs | |
State | Published - Jun 2009 |
Externally published | Yes |
Keywords
- 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