Re-examining externalizing polygenic risks and psychosocial environments: Are gene-environment correlations really...

Gene-environment correlations (rGEs) are often observed for psychiatric traits, including externalizing problems. Some researchers believe rGEs reflect the effects of offspring genotype on psychosocial environments. Others consider rGEs to be a nuisance, reflecting effects of confounders, such as population stratification, assortative mating, or parental genotypes. Our study aims to examine whether rGEs persist when confounding effects are controlled for in a family-based design.

We examined rGEs between a polygenic score (PGS) for externalizing problems and adolescent psychosocial environments (parent- and child-reported parental relationships, delinquent peer affiliation, and school connectedness) in the National Longitudinal Study of Adolescent to Adult Health. We estimated rGEs within 777 families (1,589 twins/full-siblings) and also at the population-level using 7,635 unrelated individuals.

rGEs were observed with parental relationships, delinquent peer affiliation, and school connectedness in the population sample. In family-based analyses, rGEs with parental relationships persisted at the within-family level. However, rGE with delinquent peer affiliation was attenuated and non-significant at the within-family level, suggesting the presence of confounding. Analyses regarding school connectedness were inconclusive.

While PGSs are often associated with psychosocial environments, some of these associations may be subject to substantial confounding. Our findings highlight the importance of testing rGE while controlling for potential confounds in large population-based studies.