I have of late-but wherefore I know not-lost all my mirth, foregone all custom of exercises, and indeed it goes so heavily with my disposition that this goodly frame, the earth, seems to me a sterile promontory .... Hamlet, in Hamlet, Act II, Sc. 2. The numbers may have been fewer in Shakespeare's time, but the symp­ toms were the same. Now, each year, millions instead of thousands of people suffer from a clinical depression severe enough for them to seek help from medical and mental health practitioners. Depression is the most common of all psychiatric disorders and affects people of all ages-from childhood to senescence. Since it represents a major medi­ cal, public health, and social problem for our culture, it is vitally impor­ tant that physicians and mental health professionals of all disciplines have a current and thorough understanding of various aspects of the illness-its etiologies, biology, dynamics, course, treatment, and, in some cases, its long-term management. Depression has long been known to Western civilization with early references to it dating back to Homeric writings. In subsequent times, works of art have often portrayed individuals suffering from depression, and medical tomes have proposed a host of therapies, most of which are antiquated. Over time, however, our knowledge has steadily grown.