Second, our observations that parental relationship discord and divorce mediated genetic influences on a range of alcohol outcomes across generations were robust to another highly plausible mediational path through parental alcohol use behaviors. Extended twin family and adoption studies have repeatedly shown that parental alcohol use behaviors capture genetic and environmental risk for offspring49. Using molecular genetic data, which permits the decomposition of parental genotypes into alleles that are transmitted and nontransmitted, we built on prior evidence from latent genetic studies to demonstrate that parents’ own alcohol use behaviors represent a type of environmental inheritance. In European ancestry families, nontransmitted maternal and paternal alleles for alcohol problems were associated with parental AUD clinical criterion counts, which were in turn associated with a greater number of AUD criteria and maximum drinks in the child generation. Maternal age at first intoxication also mediated the effects of nontransmitted maternal alleles on children’s age at first intoxication.
