Sixth, our environmental moderator (romantic relationship status) captures only one of many relationship features previously implicated in studies of gene-environment interplay for alcohol use and problems (Jarnecke and South, 2014), and our measure of it was rather crude. Although we detect modest evidence that SNPs in DHSs were enriched for G × E effects, we note that these statistical interactions do not in themselves illuminate the biological processes through which these effects occur. Furthermore, as with all studies of G×E with measured genotypes, power is a concern and the results should be interpreted with appropriate caution. We conducted post-hoc power analyses using Quanto (Gauderman, 2002), and when the G×E effect was very small (R2 = 0.0005), we had very low power to detect effects (12%). However, when the G×E effect was somewhat larger (R2 = 0.005) we had 72% power to detect interactions. On a more conceptual level, we note that previous analyses using the FinnTwin12 data have established latent G×E effects for relationship status and intoxication frequency (Barr et al., in press). This gives us more confidence in the
