Which mood disorder is characterized by alternating episodes of high and low mood?

Bipolar disorder is characterized by alternating episodes of high and low moods, which are known as manic and depressive episodes. During a manic episode, an individual may experience elevated mood, increased energy, and possibly impulsive behavior. Conversely, during a depressive episode, the person may feel sad, lethargic, and lose interest in activities they once enjoyed. This cyclical nature of mood fluctuations distinguishes bipolar disorder from other mood disorders, such as major depression, which typically involves only depressive episodes without the manic phase.

In contrast, schizophrenia is a serious mental health condition primarily characterized by disruptions in thought processes, perceptions, emotional responsiveness, and social interactions, rather than mood changes. Anxiety disorders are focused on excessive fear or anxiety and do not involve the mood swings seen in bipolar disorder. Major depression, while it involves low mood, does not incorporate the high mood episodes that are a hallmark of bipolar disorder. Therefore, the defining characteristic of alternating moods distinctly identifies bipolar disorder as the correct answer.