Bipolar disorder is a mood disorder characterized by periods of abnormally elevated mood (mania or hypomania) alternating with periods of depression. It affects about 5 million Americans or 3% of adults. There are several types of bipolar disorder defined by the severity of mood episodes experienced. While the causes are unclear, genetic and environmental factors likely play a role. Symptoms include dramatic shifts in mood and energy levels that impair functioning. Long-term pharmaceutical and psychosocial treatment is needed to manage symptoms and prevent relapse. The disorder carries risks such as self-harm and suicide, so ongoing treatment is important.