Bipolar disorder is notable for which of the following?

Bipolar disorder is characterized by significant mood fluctuations that include alternating episodes of mania and depression. During manic episodes, individuals may experience elevated mood, increased energy, and impulsive behavior, while depressive episodes can cause feelings of deep sadness, fatigue, and a loss of interest in activities. This cycling between manic and depressive phases is a hallmark feature of bipolar disorder, distinguishing it from other mental health conditions.

The other choices describe symptoms associated with different disorders: extreme focus on body weight relates to eating disorders such as anorexia nervosa; overeating followed by purging is characteristic of bulimia nervosa; and intense fear of social interaction is a primary symptom of social anxiety disorder. Each of these has distinct diagnostic criteria that do not involve the mood fluctuations central to bipolar disorder.