Which statement differentiates Bipolar I from Bipolar II?

• A. Bipolar I requires depressive episodes only, Bipolar II requires manic episodes
• B. Bipolar I includes manic episodes, Bipolar II includes depressive and hypomanic episodes
• C. Bipolar II includes full manic episodes
• D. Bipolar I and Bipolar II have identical criteria

Answer: (B)

The key idea is the nature of the mood episodes that define each disorder. In Bipolar I, the defining feature is a manic episode—an abnormally elevated or irritable mood with increased energy lasting at least a week (or shorter if hospitalization is needed), often with marked impairment. Depressive episodes can occur but are not required for the diagnosis. In Bipolar II, the pattern is different: there are at least one hypomanic episode plus at least one major depressive episode, and there is never a full manic episode. Hypomania is milder than mania and does not cause the same level of impairment as mania, but it still represents a distinct phase.

So the best statement is that Bipolar I includes manic episodes, while Bipolar II includes depressive and hypomanic episodes. The other options mischaracterize the criteria—for example, Bipolar I is not defined by depressive episodes only, Bipolar II does not include full manic episodes, and the two conditions do not have identical criteria.