Bipolar II disorder is primarily characterized by which of the following?

Bipolar II disorder is primarily characterized by the presence of hypomanic episodes and major depressive episodes. Hypomania is a less severe form of mania that does not lead to significant impairment in social or occupational functioning and is not associated with psychotic features. The depressive episodes in Bipolar II can be quite severe and can significantly impact a person's life.

In contrast, Bipolar I disorder is distinguished by the occurrence of at least one full manic episode, which can lead to marked impairment in functioning or necessitate hospitalization. Rapid cycling refers to experiencing four or more mood episodes (either depressive, hypomanic, or manic) in a 12-month period and can occur in both types of bipolar disorder but is not a defining feature of Bipolar II itself. Chronic mild depression may describe conditions like persistent depressive disorder but does not accurately capture the pattern of episodes seen in Bipolar II disorder. Thus, the emphasis is on the combination of hypomania and depressive episodes as the hallmark of Bipolar II.