Maternal education and prenatal smoking associations with adolescent executive function are substantially confounded by genetics.

Twin studies have suggested extremely high estimates of heritability for adolescent executive function, with no substantial contributions from shared environment. However, developmental psychology research has found significant correlations between executive function outcomes and elements of the environment that would be shared in twins. It is unclear whether these seemingly contradictory findings are best explained by genetic confounding in developmental studies or limitations in twin studies, which can potentially underestimate shared environment. In this study, we use genetic and phenotypic data from 5,939 participants, 4,827 participant mothers, and 2,903 participant fathers in the Millennium cohort to examine the role of genetics in explaining common environmental associations with executive function, assessed by the spatial working memory (SWM) task and Cambridge Gambling task. Bivariate genome-wide complex trait analysis (GCTA) revealed that single-nucleotide polymorphism effects were the sole significant predictor of the association between SWM and both maternal education and prenatal smoking. maternal GCTA and trioGCTA also found no significant evidence of indirect genetic effects on SWM, indicating that genetic nurture is unlikely to explain the bivariate GCTA results. The Cambridge Gambling task showed no significant single-nucleotide polymorphism heritability, suggesting that genetic influences on hot executive function may differ significantly from those on cool executive function. This study supports the twin study claim that the working memory component of executive function is primarily a genetic trait with minimal influence from shared environment, emphasizing the importance of using genetically sensitive designs to ensure that genetic confounding does not falsely inflate estimates of environmental influences on traits. (PsycInfo Database Record (c) 2025 APA, all rights reserved).