The relation of sleep-wake patterns to seasonal depressive behavior.

A sample of 1644 adults in Alaska, Chukotka, Yakutiya, Western Siberia and Turkmenistan were surveyed to examine the relationship between seasonal depressive behavior and sleep-wake patterns. Interviews included items derived from the Seasonal Pattern Assessment Questionnaire, a 20 item general depression scale, and a 40 item sleep-wake questionnaire designed to assess the underlying mechanisms which regulate the cycles of sleep and wakefulness. Results show that subjects who suffer from seasonal depressive behavior, at latitudes ranging from 38-66 degrees North, are characterized by a sleep-wake pattern including 1) difficulty waking in the morning, 2) a low capacity to be awake at unusual times (out of sync with normal circadian patterns) and 3) a lower quality of nighttime sleep. Subjects with high levels of general depression suffer many of the same sleep problems, but this is not due to the measured association between seasonality and other depression. Disturbances in sleep-wake patterns may help to expand our understanding of the pathogenesis of seasonal depressive behavior, but further research to differentiate it from general depression is required.