Effects of light treatment on circadian rhythmicity in seasonal affective disorder

Summary Twelve outpatients with seasonal affective disorder were treated by 1-h morning bright light exposure for 5 days. The light treatment intervention produced a significant phase advance of self-rated sleepiness rhythm, a significant decrease of the mean level of subjective sleepiness, and a significant reduction of depression scores. No significant objective circadian rhythm phase shift nor amplitude changes would account for the antidepressant effect.