The mood disorders are any disorder that can cause an increased or decreased mood. Most of the major mood disorders are characterized by the presence of one or more syndromes: a depressive episode, a manic episode, a hypomanic episode or a mixed episode.
Disorders that affect only one pole are sometimes called “unipolar disorders.” In theory these could affect either pole, however, in practice this term generally refers to depressive disorders.
The unipolar mood disorders include Major Depressive Disorder, Dysthmia, and the Secondary Depressions.
Bipolar Disorders can cause both euphoria and dysphoria. Disorders in this category include Bipolar Disorder, Cyclothymia, and the Secondary Manias.