Finally, one SNP showing an epistatic effect has known functionality. The smallest interaction P-value involved SNPs rs17588403 and rs1573496, a non-synonymous coding SNP in ADH7 with main effects predicting decreases in max drinks and number of DSM-IV symptoms, although these effects are not statistically significant. This SNP also shows evidence for interaction with two other SNPs in ADH7. One of these, rs284784, predicts a nominally significant decrease in max drinks (P = 0.04), raising the possibility that both minor alleles are required to significantly change ADH7 activity.
