What distinguishes Bipolar I disorder from Bipolar II disorder?

• A. Bipolar I requires at least one manic episode.
• B. Bipolar II requires at least one manic episode.
• C. Bipolar I has depressive episodes only.
• D. Bipolar II has no depressive episodes.

Answer: (A)

The key idea is that a full manic episode defines Bipolar I, while Bipolar II is characterized by hypomanic episodes plus depressive episodes, with no manic episode ever occurring.

A manic episode is a distinct period of abnormally elevated, expansive, or irritable mood with increased energy, lasting at least seven days (unless hospitalization is needed sooner) and causing significant impairment. It often comes with features like inflated self-esteem, decreased need for sleep, pressured speech, racing thoughts, distractibility, and risky behaviors. Because of this level of impairment, mania signals the more severe end of the spectrum, which is Bipolar I. Depressive episodes can occur in Bipolar I but are not what defines the disorder.

Bipolar II, on the other hand, involves at least one hypomanic episode and at least one major depressive episode, but never a full manic episode. Hypomania shares similar symptoms with mania but is milder and does not cause the marked impairment or hospitalization that mania does.

So the distinguishing factor is the presence of a full manic episode in Bipolar I. The other statements misstate the criteria: Bipolar II does involve depressive episodes; it does not require mania; and Bipolar I is not defined by depressive episodes alone.