A depressed or sad mood is a normal reaction to disappointment or loss; indeed, as with anxiety, it may hold survival advantages. Most mammals seem capable of depression in reaction to loss, and depression may reinforce the development of social bonds between infant and mother due to the fear of separation; it may foster social communication about negative experiences and thereby support social learning and group behavior. It may also serve more direct physiological or intrapsychic functions of protection through withdrawal (5). Such situational depression should not, however, be confused with disorders of mood, in which the person suffers intense mental, emotional, and physical anguish and substantial disability. The two probably differ in kind, and certainly differ in seriousness; the worst outcome of major depression is suicide.