Bipolar disorder is a chronic, recurrent biological condition characterized by alternating periods of mania, hypomania, depression, or a mix of symptoms. It has a lifetime prevalence of 5.1% in the United States and typically emerges between ages 18-30. Bipolar disorder is associated with substance abuse, anxiety disorders, and personality disorders. While its causes are biological in nature, psychological and environmental factors can trigger mood episodes. Treatment involves medication management, psychotherapy, and lifestyle changes to prevent relapse and limit the severity of future mood episodes.