Which statement correctly differentiates bipolar I and bipolar II?

• A. Bipolar I requires two depressive episodes; Bipolar II requires manic episodes.
• B. Bipolar I requires at least one manic episode; Bipolar II requires at least one hypomanic episode and one major depressive episode, with no full manic episode.
• C. Bipolar I includes only hypomania; Bipolar II includes mania.
• D. Bipolar I never has depressive episodes.

Answer: (B)

Differentiating bipolar I and bipolar II comes down to the nature of the mood episodes that define each disorder. Bipolar I is diagnosed when there has been at least one manic episode, which is a distinct period of abnormally elevated, expansive, or irritable mood with increased energy that lasts at least a week (or any duration if hospitalization is needed) and includes multiple accompanying symptoms, such as inflated self-esteem, decreased need for sleep, pressured speech, racing thoughts, distractibility, goal-directed activity, and risky behaviors. This manic state is the defining feature and can be severe enough to require hospitalization or include psychotic features.

Bipolar II, on the other hand, is diagnosed when there has been, at minimum, one hypomanic episode and one major depressive episode, and there has never been a full manic episode. Hypomania shares similar symptoms with mania but is milder, lasts at least four consecutive days, and does not cause marked impairment or psychosis. A major depressive episode involves a period of at least two weeks with depressed mood or anhedonia plus several related symptoms (such as sleep changes, appetite changes, fatigue, feelings of guilt or worthlessness, trouble concentrating, and possible suicidality).

So, the best statement is that bipolar I requires at least one manic episode, while bipolar II requires at least one hypomanic episode plus one major depressive episode, with no full manic episode occurring. Some distractors blur these distinctions by misstating the needed episodes or by implying mania isn’t possible in bipolar II, which isn’t correct.