Fig. 1: Characteristic fluctuations in two main types of bipolar disorder (BD).

In BD type 1, patients experience at least one manic episode and various depressive episodes, whereas in BD type 2 they undergo at least one depressive episode and at least one hypomanic episode and have no history of manic episodes. A patient with type I or type II BD with “mixed features” consist of the co-occurrence either of hypomanic/manic episodes with 3 or more depressive symptoms or depressive episodes with 3 or more hypomanic/manic symptoms.