This section will describe the common symptoms of the disease, but bear in mind that there are a wide variety of clinical presentations of the disorder. A person with bipolar disorder experiences mood episodes. These mood episodes can include depressive episodes, manic episodes, and mixed episodes. During depressive episodes, individuals usually experience sad mood, diminished interest in usual activities, and disturbances in sleep, appetite, energy, and concentration. Manic episodes typically involve either extremely happy or irritable mood, accompanied by other changes in behavior, such as increased activity, decreased need for sleep, grandiose thinking, and racing thoughts.
Mixed episodes involve the simultaneous occurrence of depressive and manic symptoms.
The duration of mood episodes typically lasts from a couple of hours to many months. Between episodes people with bipolar disorder often return to their usual functioning and personality. Some people with the disorder can enjoy healthy, stable mood for many years between episodes, while others rapidly go in and out of mood episodes almost continually, while still others experience mood episodes at frequencies between these two extremes. There is some evidence that there might be some common genetic causes of schizophrenia and bipolar disorder. This is not too surprising, since there is symptom overlap between the two disorders as well.