Which of the following is classified as a mood disorder?

Bipolar Disorder is classified as a mood disorder due to its characteristic features that involve significant changes in an individual's mood, energy levels, and activity levels. It is marked by episodes of mania or hypomania, where individuals may feel extremely energetic, euphoric, or irritable, alternating with periods of depression. These fluctuations in mood can significantly affect a person's daily functioning and overall quality of life.

In contrast, Generalized Anxiety Disorder focuses primarily on excessive anxiety and worrying, while Obsessive-Compulsive Disorder involves intrusive thoughts and repetitive behaviors, both of which do not primarily center around mood. Paranoid Personality Disorder is characterized by persistent and pervasive distrust and suspicion of others, which is categorized under personality disorders rather than mood disorders. Therefore, among the options provided, Bipolar Disorder is the only condition that fits the criteria for a mood disorder.