To determine whether the National Adult Reading Test (NART) would provide a valid estimate of premorbid intelligence in schizophrenia, two schizophrenic samples were recruited, one consisting of 35 patients resident in long-stay wards, the other of 29 patients normally resident in the community. Schizophrenic patients were individually matched for age, sex, and education with a healthy, normal subject. Both schizophrenic samples scored significantly lower on the Wechsler Adult Intelligence Scale (WAIS) than their respective control groups. NART-estimated IQ did not differ significantly between the community-resident schizophrenics and their controls, suggesting that the NART provides a valid means of estimating premorbid intelligence in such a population. NART-estimated IQ was significantly lower in the long-stay sample than in their controls. Although low NART scores in this latter sample could be a valid reflection of low premorbid IQ, the alternative explanation that NART performance was impaired by onset of the disease cannot be ruled out.

The purpose of the study reported here was to build regression equations for the estimation of premorbid IQ from demographic variables in a UK population. Subjects (n=151) free of neurological, psychiatric or sensory disability, were administered the Wechsler Adult Intelligence Scale (WAIS) and had their demographic details recorded (age, sex, occupation and education). WAIS Full Scale (FSIQ), Verbal (VIQ), and Performance IQ (PIQ) were regressed on the demographic variables. The regression equations generated by this procedure predicted 50, 50, and 30 percent of the variance in FSIQ, VIQ, and PIQ respectively. These equations should provide a convenient and useful supplement to psychometric estimates of premorbid IQ. Unlike psychometric estimates, demographic estimates are entirely independent of a patient's current cognitive status.

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