To examine potential gene-gene interactions, we examined pairwise combinations of SNPs. Several significant interactions were detected (Table 2). The most significant interaction occurred between rs4293896 of HOMER1 and rs265973 of DRD1 (OR=0.5524, P=0.007), but neither of these markers were significant at the single locus level suggesting that the combination of these two SNPs played a role in disease risk together, rather than alone. This interaction appeared to be driven by the Caucasian subjects, however, given that when the cohort was separated along racial categories, this interaction was only significant in Caucasians (OR=0.5263, P=0.044) but not in African-Americans (OR=0.6305, P=0.178) (Table 2).
