title: Neurocognitive dysfunction in bipolar and schizophrenia spectrum disorders depends on history of psychosis rather than diagnostic group.
abstract: OBJECTIVE
  Neurocognitive dysfunction is milder in bipolar disorders than in schizophrenia spectrum disorders, supporting a dimensional approach to severe mental disorders. The aim of this study was to investigate the role of lifetime history of psychosis for neurocognitive functioning across these disorders. We asked whether neurocognitive dysfunction in bipolar and schizophrenia spectrum disorders depends more on history of psychosis than diagnostic category or subtype.
  
  
  METHODS
  A sample of individuals with schizophrenia (n=102), schizoaffective disorder (n=27), and bipolar disorder (I or II) with history of psychosis (n=75) and without history of psychosis (n=61) and healthy controls (n=280), from a large ongoing study on severe mental disorder, were included. Neurocognitive function was measured with a comprehensive neuropsychological test battery.
  
  
  RESULTS
  Compared with controls, all 3 groups with a history of psychosis performed poorer across neurocognitive measures, while the bipolar group without a history of psychosis was only impaired on a measure of processing speed. The groups with a history of psychosis did not differ from each other but performed poorer than the group without a history of psychosis on a number of neurocognitive measures. These neurocognitive group differences were of a magnitude expected to have clinical significance. In the bipolar sample, history of psychosis explained more of the neurocognitive variance than bipolar diagnostic subtype.
  
  
  CONCLUSIONS
  Our findings suggest that neurocognitive dysfunction in bipolar and schizophrenia spectrum disorders is determined more by history of psychosis than by Diagnostic and Statistical Manual of Mental Disorders (Fourth Edition) diagnostic category or subtype, supporting a more dimensional approach in future diagnostic systems.
authors.affiliation: Department of Psychology, University of Oslo, 0317 Oslo, Norway. c.e.simonsen@medisin.uio.no
authors.forename: Carmen
authors.initials: C
authors.lastname: Simonsen
authors.forename: Kjetil
authors.initials: K
authors.lastname: Sundet
authors.forename: Anja
authors.initials: A
authors.lastname: Vaskinn
authors.forename: Astrid B
authors.initials: AB
authors.lastname: Birkenaes
authors.forename: John A
authors.initials: JA
authors.lastname: Engh
authors.forename: Ann
authors.initials: A
authors.lastname: Faerden
authors.forename: Halldóra
authors.initials: H
authors.lastname: Jónsdóttir
authors.forename: Petter Andreas
authors.initials: PA
authors.lastname: Ringen
authors.forename: Stein
authors.initials: S
authors.lastname: Opjordsmoen
authors.forename: Ingrid
authors.initials: I
authors.lastname: Melle
authors.forename: Svein
authors.initials: S
authors.lastname: Friis
authors.forename: Ole A
authors.initials: OA
authors.lastname: Andreassen
mesh_terms: D000328:Adult; D001714:Bipolar Disorder / Q000175:diagnosis / Q000523:psychology*; D003071:Cognition; D005260:Female; D006801:Humans; D008297:Male; D008570:Memory, Short-Term; D008875:Middle Aged; D009483:Neuropsychological Tests; D011569:Psychiatric Status Rating Scales; D011618:Psychotic Disorders / Q000175:diagnosis / Q000523:psychology*; D012559:Schizophrenia / Q000175:diagnosis; D012565:Schizophrenic Psychology; D013060:Speech; D014706:Verbal Learning