Bipolar disorder or bipolar affective disorder, historically known as manic-depressive disorder, is a psychiatric diagnosis that describes a category of mood disorders defined by the presence of one or more episodes of abnormally elevated energy levels, cognition, and mood with or without one or more depressive episodes. The elevated moods are clinically referred to as mania or, if milder, hypomania. Individuals who experience manic episodes also commonly experience depressive episodes, or symptoms, or a mixed state in which features of both mania and depression are present at the same time. These events are usually separated by periods of "normal" mood; but, in some individuals, depression and mania may rapidly alternate, which is known as rapid cycling. Severe manic episodes can sometimes lead to such psychotic symptoms as delusions and hallucinations. The disorder has been subdivided into bipolar I, bipolar II, cyclothymia, and other types, based on the nature and severity of mood episodes experienced; the range is often described as the bipolar spectrum.
Estimates of the lifetime prevalence of bipolar disorder vary, with studies typically giving values of the order of 1%, with higher figures given in studies with looser definitions of the condition. The onset of full symptoms generally occurs in late adolescence or young adulthood. Diagnosis is based on the person's self-reported experiences, as well as observed behavior. Episodes of abnormality are associated with distress and disruption and an elevated risk of suicide, especially during mixed and depressive episodes. In some cases, it can be a devastating long-lasting disorder. In others, it has also been associated with creativity, goal striving, and positive achievements. There is significant evidence to suggest that many people with creative talents have also suffered from some form of bipolar disorder. It is often suggested that creativity and bipolar disorder are linked.