Differential features between bipolar I and bipolar II disorder

Although bipolar II disorder is generally Viewed as a mild form of classic manic-depressive illness, recent investigations suggest that it could be a valid diagnostic category different from bipolar I in genetic, biological, clinical, and pharmacological aspects. Twenty-two patients fulfilling Research Diagnostic Criteria for the diagnosis of bipolar II disorder and 38 bipolar I patients were evaluated with the Schedule for Affective Disorders and Schizophrenia by two independent interviewers and compared, Bipolar II patients had significantly more previous episodes (P=.001), including both depressive (P=.003) and hypomanic (P=.006) switches, but had been hospitalized (P=.001) and presented psychotic symptoms (P<.001) less frequently, These results suggest that bipolar II disorder is less severe than bipolar I with regard to symptom intensity, but is more severe with respect to episode frequency. Copyright (C) 1997 by W.B. Saunders Company.