Superior intellectual ability in schizophrenia: neuropsychological characteristics.
OBJECTIVE
It has been suggested that neurocognitive impairment is a core deficit in schizophrenia. However, it appears that some patients with schizophrenia have intelligence quotients (IQs) in the superior range. In this study, we sought out schizophrenia patients with an estimated premorbid Intelligence Quotient (IQ) of at least 115 and studied their neuropsychological profile.


METHODS
Thirty-four patients meeting diagnostic criteria for schizophrenia or schizoaffective disorder, as defined by the Diagnostic and Statistical Manual of Mental Disorders (4th ed.; DSM-IV), with mean estimated premorbid IQ of 120, were recruited and divided into two subgroups, according to whether or not their IQ had declined by at least 10 points from their premorbid estimate. Their performance on an extensive neuropsychological battery was compared with that of 19 IQ-matched healthy controls and a group of 16 "typical" schizophrenia patients with estimated premorbid IQ <110, using one way ANOVAs and profile analysis using MANOVAs.


RESULTS
Schizophrenia patients whose estimated premorbid and current IQ both lay in the superior range were statistically indistinguishable from IQ-matched healthy controls on all neurocognitive tests. However, their profile of relative performance in subtests was similar to that of typical schizophrenia patients. Patients with superior premorbid IQ and evidence of intellectual deterioration had intermediate scores.


CONCLUSIONS
Our results confirm the existence of patients meeting DSM-IV diagnostic criteria for schizophrenia who have markedly superior premorbid intellectual level and appear to be free of gross neuropsychological deficits. We discuss the implications of these findings for the primacy of cognitive deficits in schizophrenia.
Department of Psychosis Studies, Institute of Psychiatry, King's College London, De Crespigny Park, London, SE5 8AF, United Kingdom. james.maccabe@kcl.ac.uk
James H
JH
MacCabe
Gildas
G
Brébion
Abraham
A
Reichenberg
Taposhri
T
Ganguly
Peter J
PJ
McKenna
Robin M
RM
Murray
Anthony S
AS
David
D000328:Adult; D016022:Case-Control Studies; D003072:Cognition Disorders / Q000523:psychology*; D056344:Executive Function; D005260:Female; D006801:Humans; D007360:Intelligence; D007361:Intelligence Tests; D008297:Male; D008568:Memory; D008875:Middle Aged; D009483:Neuropsychological Tests; D011618:Psychotic Disorders / Q000503:physiopathology* / Q000523:psychology*; D011930:Reaction Time; D012559:Schizophrenia / Q000503:physiopathology*; D012565:Schizophrenic Psychology