Neurocognitive dysfunction in bipolar and schizophrenia spectrum disorders depends on history of psychosis rather than diagnostic group.
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.
Simonsen
Carmen
C
Department of Psychology, University of Oslo, 0317 Oslo, Norway. c.e.simonsen@medisin.uio.no
Sundet
Kjetil
K
Vaskinn
Anja
A
Birkenaes
Astrid B
AB
Engh
John A
JA
Faerden
Ann
A
Jónsdóttir
Halldóra
H
Ringen
Petter Andreas
PA
Opjordsmoen
Stein
S
Melle
Ingrid
I
Friis
Svein
S
Andreassen
Ole A
OA
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