Polygenic Risk for Schizophrenia, Brain Structure, and Environmental Risk in UK Biobank

Schizophrenia is a heritable neurodevelopmental disorder characterized by neuroanatomical changes in the brain, but exactly how increased genetic burden for schizophrenia influences brain structure is unknown. Similarly, how environmental risk factors for schizophrenia impact brain structure is not fully understood. Here we investigated how genetic burden for schizophrenia (indexed by a polygenic risk score, PRS-SCZ) was associated with cortical thickness (CT), surface area (SA), cortical volume (CV), and subcortical structures within 18 088 White British ancestry participants with derived brain phenotypes from UK Biobank. We also explored whether environmental risk factors for schizophrenia (childhood trauma, cannabis use, birth weight, season of birth, and Townsend social deprivation index) exacerbated the impact of PRS-SCZ on brain structure. We found that PRS-SCZ was associated with lower CT in the frontal lobe, insula lobe, lateral orbitofrontal cortex, medial orbitofrontal cortex, posterior cingulate cortex, and inferior frontal cortex, and reduced SA and CV in the supramarginal and superior temporal cortex, but not with subcortical volumes. When models included environmental risk factors as covariates, PRS-SCZ was only associated with lower SA/CV within the supramarginal cortex, superior temporal cortex, and inferior frontal cortex. Moreover, no interactions were observed between PRS-SCZ and each of the environmental risk factors on brain structure. Overall, we identified brain structural correlates of PRS-SCZ predominantly within frontal and temporal regions and some of these associations were independent of environmental risk factors, suggesting that they may represent vulnerable biomarkers of genetic risk for schizophrenia. Future research is warranted to establish these associations beyond older White British individuals.