Also known as manic-depressive illness, bipolar disorder is a serious mental illness in which an individual experiences extreme mood swings and radical changes in energy levels. The condition involves cycles of mania and depression that typically recur throughout the person's lifetime. Between these manic and depressive episodes, most people with bipolar disorder are free of symptoms; however, bipolar disorder is a long-term illness that must be carefully managed throughout a person's life. During periods of severe depression or mania, a person with bipolar disorder may experience symptoms of psychosis, including delusions (which are false personal beliefs that are not subject to reason or contradictory evidence and are not explained by a person's cultural concepts) and hallucinations (in which a person hears, sees, or otherwise senses the presence of stimuli that are not there).