According to previously reported findings, exploratory interaction analyses were conducted with the DRD4 48 bp VNTR (for genotype grouping and analysis description see Methods section). The DRD4 7-repeat allele × severity of abuse interaction analysis did not yield a significant result (p = 0.43). Nor did the DRD4 7+ × DRD2 A1+ interaction analysis result in a significant finding (p = 0.725). There was a nominally significant finding at the DRD4 7+ × DAT1 9+ interaction (p = 0.045), but this result did not remain significant after correcting for multiple testing.
