0 NE of the most ubiquitous phenomena of man’s affective experiences is the disorder of mood called depression. Depression is a normal emotional response to a loss, such as a loss of a close interpersonal relationship, of prestige and position, of finances, or similar experiences. In addition depression is probably the most common of psychiatric symptoms, being associated with many psychiatric conditions and various types of physical disease. The symptom of depression can occur at any age, although it is difficult to recognize this during infancy and childhood. Definite depressive illnesses occurring in adolescence, adulthood, and during the senium have been described and are the subject of this presentation. The primary symptom of depressive illness is the generally depressed affect of the individual. This varies considerably with the type of depressive illness, the personality make-up of the patient, his emotional defense patterns, and the nature of the precipitating factors. Often mild depressive symptoms are not overtly expressed by the individual in that his depressive preoccupations are suppressed from others, and therefore may be difficult to detect. However, indications of the depression are usually manifest in some patterns of behavior such as a general pessimistic attitude, hopelessness about the future, vague somatic complaints, fatigue, loss of sleep, appetite, and weight, difficulty in concentration, and disturbed psychomotor activity, such as either retardation or agitation. These symptoms may develop acutely and persist for a short time or occur in chronic form. The thoughts of the individual dwell on feelings of self-blame, worthlessness, self-abnegation, and frequently suicide. Associated physiologic phenomena are often of considerable significance and include such things as blurring of vision, dryness of the mouth, anorexia, constipation, general fatigue, and sometimes such symptoms as amenorrhea in women or failure of potency in men.