Since dopaminergic polymorphisms have been associated with alcohol and drug abuse, we checked for possible confounding genetic association with substance abuse in our sample. Among the young adults 38.4% were diagnosed with substance abuse (Table 1). At the DRD2 SNPs the association of the TaqIA polymorphism with substance abuse was marginally significant using the 3 genotype categories (χ2 = 5.34, df = 2, p = 0.069) and nominally significant for the A1+ vs A1- categories (χ2 = 4.52, df = 1, p = 0.034), with 57.9% of the substance abuse present group carrying the A1-allele vs 36.1% of the substance abuse absent group. Similar findings emerged at the TaqIB 3 genotype categories: χ2 = 5.07, df = 2, p = 0.079, and at the B1+ vs B1- categories: χ2 = 4.21, df = 1, p = 0.04, with 39.5% of the substance abuse present group carrying the B1-allele vs 20.3% of the substance abuse absent group. These results did not remain significant after correcting for multiple testing. None of the DRD4 promoter SNPs showed significant association with substance abuse using either the 3 or 2 genotype categories.
