Depression is a common problem in older patients and a significant contributor to morbidity and mortality in this population. The identification and treatment of depression is more complex in older patients because of difficulty in diagnosis, coexisting illnesses, and concurrent drug therapy. In addition, a variety of medical conditions and drugs can cause depression. Treatment often has to be modified in consideration of other illnesses, medications, and the reduced ability of the elderly to metabolize drugs. Duration of treatment may be longer than with young patients because older adults may respond more slowly to antidepressants.