There was a significant 2-way time × DAT1 genotype interaction (F7, 856 = 2.79, p = 0.007) and a significant 3-way time × DAT1 gentype × OPRM1 genotype interaction (F7, 856 = 2.32, p = 0.024) for SHAS scores (epistatic interaction). As shown in figure 2, the DAT1 A9 carriers had higher SHAS scores across time points, when compared to the A10 carriers, and carriers of both DAT1A9 and OPRM1 *G alleles had the highest SHAS scores. In contrast, carriers of both DAT1A10 and OPRM1 *G alleles had lowest SHAS scores.
