Bipolar disorder is a common but serious mental illness. It is also called manic-depressive illness.
Bipolar disorder causes extreme changes in mood, thinking, and behavior.
At times you may feel extremely happy or irritable. At other times you may feel deeply depressed. An episode of mania or depression usually lasts for months if it is not treated. Some people, however, may have both high and low episodes within hours or days. About 15 of every 1,000 people have bipolar disorder.