Bipolar disorder, or manic-depression, is a condition that is characterized by mood swings that fluctuate between periods of mania and episodes of depression. Bipolar disorder is classified according to symptom severity as bipolar disorder I, bipolar disorder II, and cyclothymic disorder.

A 2000 study reported that bipolar disorder patients had varying degrees of problems in short- and with long-term memory, speed of information processing, and mental flexibility. They also had deficits including problems with thinking and memory. Medications used for bipolar disorder, however, could have been responsible for some of these abnormalities and more research is needed to confirm or refute these findings.

(Mania: differential effects of previous depressive and manic episodes on response to treatment:Acta Psychiatr Scand 2000).