What is the primary characteristic of Bipolar II Disorder?

Bipolar II Disorder is primarily characterized by the presence of recurrent major depressive episodes accompanied by at least one episode of hypomania. In contrast to Bipolar I Disorder, where full manic episodes can occur, Bipolar II involves hypomanic episodes, which are less severe than manic episodes and do not significantly impair functioning or necessitate hospitalization.

This distinction is important because it highlights the pattern of mood fluctuations seen in individuals with Bipolar II Disorder. The recurrent major depressive episodes can be quite debilitating and contribute significantly to the clinical picture, making it essential to recognize this aspect in diagnosis and treatment.

The other options do not accurately describe Bipolar II Disorder. Chronic mild depression for at least two years more closely aligns with Persistent Depressive Disorder (Dysthymia), while alternating periods of hypomania and severe depression would suggest a different course that is characteristic of Bipolar I Disorder. Lastly, the presence of at least four mood episodes in one year might be indicative of Cyclothymic Disorder or a different classification but does not specifically define Bipolar II Disorder.