a type of depressive disease, formerly called manic-depressive illness. Not nearly as prevalent as other forms of depressive disorders. Bipolar disorder involves alternating cycles of depression and elation or mania. Sometimes the mood switches are dramatic and rapid, but most often they are gradual. Mania often affects thinking, judgment, and social behaviour in ways that cause serious problems and embarrassment. For example, unwise business or financial decisions may be made when an individual is in a manic phase. Bipolar disorder is often a chronic recurring condition.