Seasonal variation of depressive symptoms in Antarctica.

Symptom characteristics and risk factors for seasonal variation in depressive symptoms were prospectively examined in 119 men and women who overwintered in Antarctica. Over a 12-month period, this cohort reported significant increases in their global depressive symptom scores as well as several individual symptoms associated with winter depression. Summer depression and marital status were significant independent predictors of winter depression. Factor analyses of summer and winter symptoms revealed a set of symptoms traditionally associated with the winter-over experience in a distinct factor not found in summer. These results indicate that even asymptomatic, clinically normal populations experience seasonal variation in mood in high-latitude environments. However, this seasonal variation may be the result of social isolation during the winter months rather than the prolonged absence of sunlight.