Cortical thickness correlates of cognitive performance in cognitively-matched individuals with and without schizophrenia

Schizophrenia is characterized by psychosis and, in most cases, cognitive impairment. It is unclear, however, whether these elements of the disorder represent distinct or related disease processes. Accordingly, this study investigated 3-way interactions between group, cognition and cortical thickness in cognitively-matched patients with schizophrenia and healthy control groups. Patients and healthy controls were group-matched on demographics and a broadly-based index of cognitive performance. T1-weighted images were processed using Freesurfer. Variable selection techniques were applied to determine which regions best predicted 3-way interaction effects. Independent variables included age, sex, IQ, and 87 regional cortical thickness values strongly associated with group or cognition. Antipsychotic treatment effects were also investigated. Twenty regions were selected by the best fitting model. The top 6 regions included the left pre- and post-central, left superior frontal and temporal and right rostral and caudal middle frontal cortices. No antipsychotic treatment effects were seen. Cortical thinning in schizophrenia exists even in the absence of cognitive impairment. Our findings support the separation of psychosis and cognitive impairment as independent disease processes, with distinct relations with cortical thickness in prefrontal cortical areas. Parsing out these two disease processes will increase understanding of heterogeneity in schizophrenia and may modify treatment targets.