Depression (major depression) is defined as depressed mood on a daily basis for a minimum duration of 2 weeks. An episode may be characterized by sadness, indifference or apathy, or irritability and is usually associated with change in neurovegetative functions, including sleep patterns, appetite and weight, motor agitation or retardation, fatigue, impairment in concentration and decision making, feelings of shame or guilt, thoughts of death, dying or suicide. Patients with depression have a profound loss of pleasure in all enjoyable activities, exhibit early morning awakening, feel that the dysphoric mood state is qualitatively different from sadness, and often notice a diurnal variation in mood (worse in morning hours). Paradoxically, these more severe features predict a good response to antidepressant treatment.
