Why does postpsychotic IQ decline in childhood-onset schizophrenia?

Objective: The authors' goal was to examine whether the postpsychotic decline in full-scale IQ during adolescence for patients with childhood-onset schizophrenia is due to a dementing process or simply failure to acquire new information and skills. Method: Linear regression was used to determine the rate of change for scaled and raw scores on subtests of 31 patients with childhood-onset schizophrenia. The resulting slopes were examined and related to changes in the patients' brains determined by magnetic resonance imaging. Results: Three postpsychotic subtest scaled scores declined significantly: picture arrangement, information, and block design. In contrast, there was no decline in the non-age-corrected (raw) scores for any subtest. A significant correlation was found between decrease in hippocampal volume and a smaller increase in raw score on the information subtest. Conclusions: The decline during adolescence in the full-scale IQ of patients with childhood-onset schizophrenia does not reflect dementia but, rather, an inability to acquire new information and abilities.