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Schizophrenia Bulletin Advance Access published online on November 24, 2009
Schizophrenia Bulletin, doi:10.1093/schbul/sbp143
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© The Authors 2009. Published by Oxford University Press on behalf of the Maryland Psychiatric Research Center.
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.5/), which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

IQ Trajectory, Cognitive Reserve, and Clinical Outcome Following a First Episode of Psychosis: A 3-Year Longitudinal Study

Verity C. Leeson1,2,3, Pranev Sharma3, Masuma Harrison3, Maria A. Ron2, Thomas R. E. Barnes3 and Eileen M. Joyce2
2 UCL Institute of Neurology, The National Hospital for Neurology and Neurosurgery, Queen Square, London WC1N 3BG, UK
3 Department of Psychological Medicine, Imperial College London, Charing Cross Campus, St. Dunstan’s Road, London W6 8RP, UK

1 To whom correspondence should be addressed; tel: +44 (0)207 837 3611, e-mail: v.leeson{at}ion.ucl.ac.uk.

Comparison of current and estimated premorbid IQ in schizophrenia suggests that there are subgroups with low IQ, deteriorated IQ (DIQ), or preserved IQ and that this is established by psychosis onset. There are no controlled studies examining the trajectory of these IQ subgroups longitudinally or their relationship with clinical and social outcomes. Of 129 individuals with first-episode schizophrenia or schizoaffective disorder, 25% showed stable low IQ, 31% showed stable IQ in the average/high range, and 44% demonstrated intellectual deterioration by 10 points or more. Patients in the low and deteriorated groups were equally impaired on tests of memory and executive function compared with the preserved average/high-IQ group and controls and showed more negative and disorganization symptoms than the preserved average/high-IQ group. Sixty patients and 27 controls were assessed again 1 and 3 years later. There was no evidence that those with IQ deterioration at baseline continued on a declining cognitive trajectory or that those with preserved average/high IQ experienced subsequent IQ decline. The low IQ group showed no change in IQ, whereas both the DIQ and the preserved IQ groups improved. However, the rate of improvement of these 2 subgroups was no greater than that of the healthy controls, suggesting that this reflected practice effects. Both the low and the deteriorated groups had longer index admissions, more core negative symptoms, and worse occupational outcomes at 3 years. These data suggest that following psychosis onset, IQ is stable and that it is IQ at psychosis onset rather than premorbid IQ predicts a more severe illness.

Keywords: schizophrenia / cognition / trajectory / premorbid IQ / WAIS / WTAR


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