EFFECTS OF LIGHT TREATMENT ON SLEEP STRUCTURE IN SEASONAL AFFECTIVE-DISORDER

Twelve outpatients with seasonal affective disorder (depression, winte r type) were treated by 1 h of bright light exposure for five mornings . The intervention produced a significant reduction in depression scor es, but no change was seen in the sleep electroencephalographic variab les recorded after light treatment. Significant changes were seen, how ever, in ratings of subjective sleepiness. The acrophase of the circad ian sleepiness rhythm was phase advanced, the mean level of the sleepi ness rhythm was diminished, and the mean values of sleepiness scores w ere reduced at 8 and 10 a.m. This minimal influence of bright light on sleep structure is unlikely to explain the well-documented antidepres sant effect.