Any mental disorder that has a disturbance of mood as the predominant feature. In the Diagnostic and Statistical Manual of Mental Disorder, these have been divided into mood episodes, mood disorders, and specifications describing either the most recent mood episode or the course of recurrent episodes. Mood disorders, including dysthymic disorder, are divided into the depressive disorders (unipolar depression), the bipolar disorders, and two disorders based on cause, i.e., due to a general medical condition or substance-induced mood disorder. Depressive disorders are distinguished from the bipolar disorders by the absence of a history of a manic, mixed, or hypomanic episode. Bipolar I disorder and bipolar II disorder involve the presence of or history of manic episodes, mixed episodes, or hypomanic episodes, usually with a history or presence of major depressive episodes.
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