Bipolar disorder used to be known as manic depression. It is classified as a mood disorder and is characterized by at least one manic episode and typically one or more major depressive episodes. A manic episode refers to a period of at least one week where the person exhibits elevated, euphoric, or irritable mood. The person also displays symptoms of increased activity, with much higher levels of energy, initiative, and impulsivity than normal.

More specifically, three or more of the following symptoms must be present (or four if the mood is only irritable): inflated self-esteem or grandiosity; a decreased need for sleep; an increase in amount of talking or pressure to keep talking; flight of ideas or racing thoughts; distractibility; an increase in goal-directed activity; and an increase in risky, pleasurable behavior. People in manic episodes frequently engage in reckless and excessive spending, sexual activity, or substance abuse. They can also have psychotic symptoms during manic episodes, but the symptoms tend to be mood-congruent (consistent with their elevated, expansive mood). For example, they may have grandiose delusions that they are going to Washington, D.C., to run the State Department. People with bipolar disorder tend to have a higher baseline than people with schizophrenia. Many people are completely symptom-free when not in the middle of an episode and can live entirely normal lives. However, even people who are symptom-free at baseline will need to take medication to maintain their mental health.