Moreover, an interaction between PER2 genotype and exposure to severe life stress on the AUDIT score emerged. Subsequent simple regression analyses stratified for genotype demonstrated that the number of severe negative life events was associated with higher scores on the AUDIT among individuals homozygous for the A allele (B = .669, p<.001), but not among carriers of the G allele (B = −.108, p = .674). Specifically, in A homozygotes, each additional life event increased the AUDIT score by 0.669 (SE = 0.123), while not significantly decreasing the AUDIT score by 0.108 (SE = 0.268) in G carriers. Figure 1 visualizes the interaction, using a median split on the life events measure. There were no other interactions between PER2 genotype and severe life stress with regard to further drinking measures.
