Morning vs evening light treatment of patients with winter depression |
Author(s): , , , , , ,
Journal/Book: Arch Gen Psychiatry. 1998; 55: 515 N State St, Chicago, IL 60610. Amer Medical Assoc. 890-896.
Abstract: Background: According to the phase-shift hypothesis for winter depression, morning light (which causes a circadian phase advance) should be more antidepressant than evening light (which causes a delay). Although no studies have shown evening light to be more antidepressant than morning light, investigations have shown either no difference or morning light to be superior; The present study assesses these light-exposure schedules in both crossover and parallel-group comparisons. Methods: Fifty-one patients and 49 matched controls were studied for 6 weeks. After a prebaseline assessment and a light/dark and sleep/wake adaptation baseline week, subjects were exposed to bright light at either 6 to 8 AM or 7 to 9 PM for 2 weeks. After a week of withdrawal from light treatment, they were crossed over to the other light schedule. Dim-light melatonin onsets were obtained 7 times during the study to assess circadian phase position. Results: Morning light phase-advanced the dim-light melatonin onset and was more antidepressant than evening light, which phase-delayed it. These findings were statistically significant for both crossover and parallel-group comparisons. Dim-light melatonin onsets were generally delayed in the patients compared with the controls. Conclusions: These results should help establish the importance of circadian (morning or evening) time of light exposure in the treatment of winter depression. We recommend that bright-light exposure be scheduled immediately on awakening in the treatment of most patients with seasonal affective disorder.
Note: Article Lewy AJ, Oregon Hlth Sci Univ, Dept Psychiat, Sleep & Mood Disorders Lab, L-469, 3181 SW Sam Jackson Pk Rd, Portland,OR 97201 USA
Keyword(s): SEASONAL AFFECTIVE-DISORDER; PHASE-RESPONSE CURVE; HUMAN CIRCADIAN PACEMAKER; BRIGHT LIGHT; MELATONIN ONSET; THERAPY; PHOTOTHERAPY; ANTIDEPRESSANT; SHIFTS; TEMPERATURE
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