Bipolar disorder is a mood disorder that affects over 5.7 million people, including some celebrities. It involves alternating periods of mania and depression. Manic episodes involve feelings of euphoria and decreased need for sleep lasting at least a week. Depressive episodes involve overwhelming sadness. Bipolar disorder is categorized into types I and II depending on the presence of manic or hypomanic episodes. Treatment typically involves medications like lithium, anticonvulsants, and antidepressants, as well as cognitive behavioral therapy in some cases.