In the genetics of the beholder: gene-environment interplay for internalising and externalising behaviours using...

Adolescent internalising and externalising behaviours arise from a complex interplay of genetic and environmental factors. Understanding how parents' genes affect risk for psychopathology in offspring-whether through direct genetic transmission or environmentally mediated genetic nurture-is crucial for identifying causal mechanisms and intervention targets. However, few studies have examined this interplay rigorously in relation to adolescent psychopathology, and findings to date have remained mixed. To tackle this gap in research, we examined both genetic transmission and genetic nurture pathways using polygenic risk for psychopathology on adolescent internalising and externalising behaviours.The sample comprised 762 genotyped parent-offspring trios from the TRacking Adolescents' Individual Lives Survey (TRAILS). Parent and offspring polygenic scores for genetic liability to general psychopathology (p-PGS) were computed and jointly modelled to estimate genetically transmitted and genetic nurture contributions to parental reports of offspring internalising and externalising behaviours at age 11.Our findings indicate that parental polygenic risk for genetic liability to general psychopathology (captured as parental p-PGS) was associated with adolescent internalising-but not externalising-behaviours. Primarily this association was via environmental rather than direct genetic pathways, providing support for genetic nurture (b = 0.13, 95% CI = 0.05/0.22, q-value = 0.004). However, we found no association between parental p-PGS and adolescent-reported parenting behaviours, limiting our ability to assess whether genetic nurture effects for internalising problems were mediated by adolescent perspectives of parenting.The study highlights the importance of genetic nurture's influence on internalising behaviours, and encourages the consideration of genetic influences on perceptions of environmental influences that may be key.