Diurnal mood variation in major depressive disorder.

Depression disturbs mood, but a clear picture of diurnal mood rhythms in depression has yet to emerge. This study examined variations in positive affect (PA) and negative affect (NA), two dimensions of mood that generate diurnal patterns among healthy individuals. Repeated measurements of NA and PA in daily life were obtained over 6 days from 47 depressed outpatients and 39 healthy individuals using the Experience Sampling Method. Relative to healthy individuals, depressed individuals exhibited increasing PA levels during the day with a later acrophase. In contrast, depressed persons' NA exhibited a more pronounced diurnal rhythm and was more variable from moment to moment than healthy individuals'. Ambulatory mood measurements in depression suggest distinct diurnal disturbances of positive and negative affect.