We examined whether SNPs in regulatory regions were enriched for G×E effects using a chi-square test that compared the proportion of DHS SNPs among the set of SNPs with significant (p < .05) G×E effects relative to the proportion of DHS SNPs in the full genome. For these analyses we used a contemporaneous measure of alcohol misuse, intoxication frequency. We focused on a contemporaneous measure of alcohol misuse in order to ensure that our romantic relationship status environmental moderator and alcohol misuse outcome were temporally matched1. For these analyses, we selected a set of top SNPs in the ALSPAC GWAS (p < 0.005) from the set of 212,718 LD-pruned autosomal SNPs common across the ALSPAC and FinnTwin12 samples, resulting in 1137 SNPs. We focused on the set of the more highly associated SNPs in view of evidence that G×E effects are most likely to be observed for SNPs with smaller p-values (Thomas, 2010). This threshold was arbitrary, but was selected in an attempt to balance testing a large enough number of “top” SNPs with the computational resources required for such
