Intellectual differences between schizophrenic patients and normal controls across the adult lifespan.

A debate persists about whether IQ declines during the duration of schizophrenia or whether an early deficit remains static across the lifespan. To examine this, we measured estimated current IQ (Quick Test Revised: QTR) and estimated premorbid IQ (National Adult Reading Test: NART) in schizophrenic patients (n=110) and matched healthy controls (n=71) across a wide age range (20-88). Age correlated negatively with NART and QTR IQ for schizophrenic patients, but not for controls. A subset of 23 schizophrenic patients was also retested on the NART after 4 years to determine NART stability and they showed no significant change. We propose that the lower NART IQ in older patients reflects a lower 'starting point' and that this may be related to lower educational opportunities in older patients.