Depression is an illness that involves the body, mood and thoughts. It affects the way a person eats and sleeps, the way one feels about oneself and the way one thinks about things. Depression is not the same as a passing blue mood. It is not a sign of personal weakness or a condition that can be willed or wished away. People with depression cannot merely "pull themselves together" and get better. Without treatment, symptoms can last for weeks, months or years. Appropriate treatment, however, can help most people who suffer from depression.

Depressive disorders come in different forms, just as is the case with other illnesses such as heart disease. Three of the most common types of depressive disorders are major depression, dysthymia, and bipolar disorder. However, within these types there are variations in the number of symptoms, their severity, and persistence.

Many forms of psychotherapy, including some short-term (10- to 20-week) therapies, can help depressed individuals. "Talking" therapies help patients gain insight into and resolve their problems through verbal exchange with the therapist, sometimes combined with "homework" assignments between sessions. "Behavioral" therapists help patients learn how to obtain more satisfaction and rewards through their own actions and how to unlearn the behavioral patterns that contribute to or result from their depression.