Findings from a recent study suggest that brain abnormalities in first-degree relatives (FDRs) are at least partly explained by genes predisposing to both schizophrenia risk and intelligent quotient (IQ). Researchers investigated whether brain abnormalities in nonpsychotic relatives differ per type of FDR and how these abnormalities are related to IQ. 980 individuals from 5 schizophrenia family cohorts (330 FDRs, 432 controls, 218 patients) were included. Effect sizes were calculated to compare brain measures of FDRs and patients with controls, and between each type of FDR. They found:
- FDRs had significantly smaller intracranial volume (ICV), surface area, total brain, cortical gray matter, cerebral white matter, cerebellar gray and white matter, thalamus, putamen, amygdala, and accumbens volumes as compared with controls.
- Offspring showed the largest effect sizes relative to the other FDRs; however, none of the effects in the different relative types survived correction for multiple comparisons.
- After IQ correction, all effects disappeared in the FDRs after correction for multiple comparisons.
- The findings in FDRs were not explained by having a nonpsychotic disorder and were only partly explained by ICV.
- FDRs show brain abnormalities that are strongly co-varying with IQ.
de Zwarte SMC, Brouwer RM, Tsouli A, et al. Running in the family? Structural brain abnormalities and IQ in offspring, siblings, parents, and co-twins of patients with schizophrenia. [Published online ahead of print December 28, 2018]. Schizophr Bull. doi:10.1093/schbul/sby182.