A meta-analysis of data on 4,396 subjects with schizophrenia and 745,000 controls from 12 independent studies found significant decrements in premorbid IQ among individuals who later developed schizophrenia. The risk of schizophrenia increased by 3.7 percent for every point decrease in IQ, and greater premorbid IQ decrements were associated with earlier onset of illness.
The results were published online July 11 in Schizophrenia Research. IQ alone is not a measure for schizophrenia risk, but as one component among many neurodevelopmental factors, it appears to increase risk across the range of intellectual ability, researchers said.
The study contributes to a growing body of research focused on factors in psychosis risk and early identification of individuals at high risk for developing psychosis. You can read much more about these issues in Psychiatric News at http://pn.psychiatryonline.org/content/43/3/2.full and http://pn.psychiatryonline.org/content/46/10/18.1.full.