Top ten list in sleep.

Seasonal affective disorder (SAD) is a subtype of a mood disorder that is characterized by recurring episodes of major depression, the onset and remission of which seem to relate to particular seasons. This condition most commonly begins in autumn/ winter and fully remits by spring. While the pathogenesis is uncertain, there appears to be a relationship to light exposure and delay in the affected individual’s circadian rhythm. Controlled clinical trials (including the author’s previous study,1 from which some patients were included here) have demonstrated the benefit of light exposure in improving mood in those patients with SAD. Terman and colleagues monitored plasma melatonin levels, a circadian phase indicator, and depression in 42 patients with SAD. Patients were exposed to 10,000 lux light for 30 min in the evening or the morning for 10 to 14 days while depressed, within a crossover design. Results revealed that there was no difference between the mean ( SD) percentage of change in depression ratings relative to morning light exposure (58.8% 29.2%) or evening light exposure (57.9% 28.8%). However, the remission rate (depression score, 0) was higher for morning light (50% vs 40%, respectively). This study, along with the previously reported work by these authors further defines the protocol of morning light exposure in the treatment of patients with SAD.