Depression is related to the normal emotions of sadness and
bereavement, but it does not remit when the external cause of these emotions
dissipates, and it is disproportionate to their cause. Classic severe states
of depression often have no external precipitating cause. It is difficult, however, to
draw clear distinctions between depressions with and those without psychosocial
precipitating events.1 The diagnosis of major depressive disorder requires a distinct
change of mood, characterized by sadness or irritability and accompanied by at least
several psychophysiological changes, such as disturbances in sleep, appetite, or sexual
desire; constipation; loss of the ability to experience pleasure in work or with
friends; crying; suicidal thoughts; and slowing of speech and action. These changes
must last a minimum of 2 weeks and interfere considerably with work and family
relations. On the basis of this broad definition, the lifetime incidence of depression
in the United States is more than 12% in men and 20% in women.2 Some have
advocated a much narrower definition of severe depression, which they call melancholia
or vital depression.3