Genetics of educational attainment and social problem behaviors: Robust estimates of direct genetic effects.

This study examines the genetic underpinnings of (problematic) socioemotional behaviors in children (6-18 years old) by leveraging a within-family trio design using data from the Lifelines cohort (N=3,090-4,510). Socio-emotional development is key to understanding long-term educational, occupational, and mental health outcomes. Yet, their genetic foundations are not fully understood. We estimate direct genetic effects of educational attainment (EA)-related polygenic indices (PGIs), as a whole and decomposed into cognitive (Cog) and non-cognitive (NonCog) components, on a comprehensive set of internalizing and externalizing behaviors assessed via self- and parental-reported Achenbach System of Empirically Based Assessment (ASEBA) measures. Our findings reveal that higher EA-related PGIs, particularly their cognitive component, are robustly associated with lower levels of attention problems, rule-breaking, and somatic complaints. These effects persist after adjusting for parental genetics, supporting a causal interpretation. Some associations-such as those of the NonCog EA PGI with attention problems and rule-breaking, and of the full EA PGI with externalizing behaviors-lose statistical significance when parental genetics are included, suggesting that small environmentally mediated parental influences may play a role. We also find notable sex differences, with stronger associations in girls, especially for internalizing traits, and observe modest (although insignificant) differences between self- and parent-reported outcomes. Our findings contribute novel evidence that cognitive genetics influence behavioral development and highlight the value of family-based genetic designs for uncovering the complex interplay of genes and environment in socio-emotional functioning.