Bipolar disorder, also known as manic-depressive illness, is characterized by periods of depression alternating with periods of mania or hypomania. During manic episodes, patients experience elevated mood, decreased need for sleep, grandiosity, and increased goal-directed activity. Depressive episodes involve depressed mood, loss of interest, changes in appetite and sleep, feelings of worthlessness, and thoughts of death or suicide. Treatment involves medication such as mood stabilizers, antipsychotics, and antidepressants as well as psychotherapy. The causes of bipolar disorder are thought to involve genetic, neurological, environmental, and psychosocial factors.