: any of several mood disorders characterized usually by alternating episodes of depression and mania or by episodes of depression alternating with mild nonpsychotic excitement—called also bipolar affective disorder, bipolar illness, manic depression, manic-depressive illness, manic-depressive psychosis; compare major depressive disorder
Mental illness characterized by the alternation of manic and depressive states. Depression is the more common symptom, and many patients experience only a brief period of overoptimism and mild euphoria during the manic phase. The condition, which seems to be inheritable, probably arises from malregulation of the amines norepinephrine, dopamine, and 5-hydroxytryptamine. It is most commonly treated with lithium carbonate.