Premorbid IQ as a predictor for the course of IQ in first onset patients with schizophrenia: A 10-year follow-up study

van Winkel, Ruud; Myin-Germeys, Inez; Delespaul, Philippe; Peuskens, Jozef; De Hert, Marc; van Os, Jim

doi:10.1016/j.schres.2006.06.033

« Previous Next »Schizophrenia Research
Volume 88, Issue 1 , Pages 47-54, December 2006

Premorbid IQ as a predictor for the course of IQ in first onset patients with schizophrenia: A 10-year follow-up study

Ruud van Winkel
- University Psychiatric Center Katholieke Universiteit Leuven, Leuvensesteenweg 517, 3070 Kortenberg, Belgium
- Department of Psychiatry and Neuropsychology, EURON, South Limburg Mental Health Research and Teaching Network, Maastricht University, PO Box 616, 6200 MD Maastricht, The Netherlands
Inez Myin-Germeys
- Department of Psychiatry and Neuropsychology, EURON, South Limburg Mental Health Research and Teaching Network, Maastricht University, PO Box 616, 6200 MD Maastricht, The Netherlands
Philippe Delespaul
- Department of Psychiatry and Neuropsychology, EURON, South Limburg Mental Health Research and Teaching Network, Maastricht University, PO Box 616, 6200 MD Maastricht, The Netherlands
Jozef Peuskens
- University Psychiatric Center Katholieke Universiteit Leuven, Leuvensesteenweg 517, 3070 Kortenberg, Belgium
Marc De Hert
- University Psychiatric Center Katholieke Universiteit Leuven, Leuvensesteenweg 517, 3070 Kortenberg, Belgium
Jim van Os
- Department of Psychiatry and Neuropsychology, EURON, South Limburg Mental Health Research and Teaching Network, Maastricht University, PO Box 616, 6200 MD Maastricht, The Netherlands
- Division of Psychological Medicine, Institute of Psychiatry, De Crespigny Park, London SE5 8AF, UK
- Corresponding author. Department of Psychiatry and Neuropsychology, European Graduate School of Neuroscience, Maastricht University, PO Box 616 (DRT10), 6200 MD Maastricht, The Netherlands. Tel.: +31 43 3875443; fax: +31 43 3875444.

Received 14 December 2005; received in revised form 23 June 2006; accepted 24 June 2006.

Abstract

The aim of the present study was to examine the longitudinal course of IQ and its heterogeneity in patients with schizophrenia, from the perspective of the two main “subtypes” of schizophrenia described in the literature: progressive cognitive deficit versus cognitive stabilisation or recovery. Premorbid IQ scores and WAIS IQ scores of 100 first onset patients were obtained at first hospitalization (T1) and after 10 years (T2). Significant changes in IQ over time were found, representing (i) at T1, a deterioration compared to premorbid intelligence (B=−6.3, 95% CI −9.5 to −3.0, p<0.0001), followed by (ii) a recovery at T2 where IQ matched premorbid intelligence again (B=0.5, 95% CI −3.1 to 4.0, p=0.79). In addition, a significant interaction was found between course of IQ over time and estimated premorbid IQ, demonstrating that subjects with lower premorbid IQ levels remained stable over time whereas in individuals with higher premorbid IQ levels a pattern of deterioration was evident at T1, followed by a recovery up to premorbid level at T2. The data confirm the importance of estimated premorbid IQ as an indicator of the longitudinal course of cognitive functioning in patients with schizophrenia and add evidence to the hypothesis of heterogeneity or “subtypes” of schizophrenia. The data, however, do not confirm the existence of progressive deterioration of cognitive functioning. Rather, catching up of cognitive function later in the course of the illness may take place in those whose deficits become apparent in the early phases of illness, whereas those with the most severe premorbid impairments remain stable.