Depression is a mood disorder characterized by a persistent sad or empty feeling, irritability, and a loss of interest in everyday activities. The condition is twice as common in women as in men and is usually episodic. But unlike normal sadness or grieving, most bouts of depression last for weeks, months, or even years. Some people with depression have a chronic, low-grade form of the condition called dysthymia. A smaller number suffer from bipolar disorder-bouts of depression interspersed with periods of elevated (manic) mood (see Bipolar Disorder).

Although depression is usually not considered life-threatening, it can lead to thoughts of and attempts at suicide. As many as 70 percent of suicides in the United States are related to depression, and about 15 percent of severely depressed people commit suicide. Fortunately, the overwhelming majority of people with depression can be helped by counseling (psychotherapy), antidepressant drugs, or other therapies, thus lowering the suicide risk.