Schizophrenia patients with high intelligence: A clinically distinct sub-type of schizophrenia?
BACKGROUND
Schizophrenia patients are typically found to have low IQ both pre- and post-onset, in comparison to the general population. However, a subgroup of patients displays above average IQ pre-onset. The nature of these patients' illness and its relationship to typical schizophrenia is not well understood. The current study sought to investigate the symptom profile of high-IQ schizophrenia patients.


METHODS
We identified 29 schizophrenia patients of exceptionally high pre-morbid intelligence (mean estimated pre-morbid intelligence quotient (IQ) of 120), of whom around half also showed minimal decline (less than 10 IQ points) from their estimated pre-morbid IQ. We compared their symptom scores (SAPS, SANS, OPCRIT, MADRS, GAF, SAI-E) with a comparison group of schizophrenia patients of typical IQ using multinomial logistic regression.


RESULTS
The patients with very high pre-morbid IQ had significantly lower scores on negative and disorganised symptoms than typical patients (RRR=0.019; 95% CI=0.001, 0.675, P=0.030), and showed better global functioning and insight (RRR=1.082; 95% CI=1.020, 1.148; P=0.009). Those with a minimal post-onset IQ decline also showed higher levels of manic symptoms (RRR=8.213; 95% CI=1.042, 64.750, P=0.046).


CONCLUSIONS
These findings provide evidence for the existence of a high-IQ variant of schizophrenia that is associated with markedly fewer negative symptoms than typical schizophrenia, and lends support to the idea of a psychosis spectrum or continuum over boundaried diagnostic categories.
Department of Psychosis Studies, Institute of Psychiatry, King's College London, Box P063, De Crespigny Park, London, United Kingdom, SE5 8AF. Electronic address: Emma.cernis@hmc.ox.ac.uk.
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Černis
Department of Psychosis Studies, Institute of Psychiatry, King's College London, Box P063, De Crespigny Park, London, United Kingdom, SE5 8AF.
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Vassos
Unit of Research and Development, Parc Sanitari Sant Joan de Déu and CIBERSAM, Barcelona, Spain.
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Brébion
Benito Menni CASM, and CIBERSAM, Barcelona, Spain.
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McKenna
Department of Psychosis Studies, Institute of Psychiatry, King's College London, Box P063, De Crespigny Park, London, United Kingdom, SE5 8AF.
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Murray
Department of Psychosis Studies, Institute of Psychiatry, King's College London, Box P063, De Crespigny Park, London, United Kingdom, SE5 8AF.
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David
Department of Psychosis Studies, Institute of Psychiatry, King's College London, Box P063, De Crespigny Park, London, United Kingdom, SE5 8AF.
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JH
MacCabe
D000328:Adult; D003071:Cognition; D005260:Female; D006801:Humans; D007360:Intelligence; D007361:Intelligence Tests; D008297:Male; D008875:Middle Aged; D009483:Neuropsychological Tests; D012559:Schizophrenia / Q000145:classification* / Q000503:physiopathology*; D012565:Schizophrenic Psychology
Cognitive function; IQ; Psychosis; Schizophrenia; Superphrenia