The impact of residual symptoms on outcome of major depression.

Unipolar depression should be viewed as a chronic illness with multiple phases rather than as a relapsing-remitting disorder. Incomplete remission from depression is common, with approximately one third of patients continuing to have residual depression at remission. Patients who have had a depressive episode spend more time with residual depressive symptoms than with major depression long term. The presence of residual symptomatology after an episode of depression is associated with an increased risk of short-term relapse, a long-term chronic course, higher risk of suicide attempts, poor social functioning, and poor outcome of comorbid medical illnesses.