title: Differential features between bipolar I and bipolar II disorder.
abstract: 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.
authors.affiliation: Department of Psychiatry, Hospital Clínic, Barcelona, University of Barcelona, Spain.
authors.forename: E
authors.initials: E
authors.lastname: Vieta
authors.forename: C
authors.initials: C
authors.lastname: Gastó
authors.forename: A
authors.initials: A
authors.lastname: Otero
authors.forename: E
authors.initials: E
authors.lastname: Nieto
authors.forename: J
authors.initials: J
authors.lastname: Vallejo
mesh_terms: D000328:Adult; D000342:Affective Symptoms / Q000503:physiopathology; D017668:Age of Onset; D001714:Bipolar Disorder / Q000145:classification* / Q000503:physiopathology*; D016009:Chi-Square Distribution; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012008:Recurrence; D012189:Retrospective Studies; D012494:Sampling Studies; D012720:Severity of Illness Index; D009626:Terminology as Topic