A mood disorder sometimes called manic-depressive illness or manic-depression that characteristically involves cycles of depression and elation or mania. Sometimes the mood switches from high to low and back again are dramatic and rapid, but more often they are gradual and slow, and intervals of normal mood may occur between the high (manic) and low (depressive) phases of the condition. The symptoms of both the depressive and manic cycles may be severe and often lead to impaired functioning.
