(of psychiatric illness) characterized by both manic and depressive episodes, or manic ones only.

Bipolar disorder is a serious brain and behavioral disorder that’s characterized by severe changes in mood and energy. These changes affect a person’s ability to handle their day-to-day tasks. These changes in behavior, known as "mood episodes," are defined by the types of symptoms a person is experiencing: manic, depressive, or mixed. These periods of abnormal behavior are drastically different from a person's usual behavior.