Two genotyped SNPs reached genome-wide significance (p<8.4 × 10−8). A SNP in the uncharacterized gene LOC151121 on chromosome 2, rs2952621, was associated with ANYDEP (p=1.8×10−8; OR = 1.07). Secondary analysis was performed to test whether this SNP demonstrated greater evidence of association with a particular substance. Although more individuals were alcohol dependent, the pattern of dependence by genotype was similar for all 4 substances (χ(1)2 = 0.48, p=0.49; Figure 3A), indicating that the association was not driven by dependence on one particular substance. Individuals with one or two copies of the minor allele (T) were more likely to be dependent on at least one substance than those having no copies of the minor allele. Analysis of imputed SNPs in this region provided additional evidence to support the association (Figure 4A). There was modest replication for this SNP in the SAGE sample (p=0.02, OR = 1.1), with T as the risk allele in both samples. Corresponding SAGE results for the SNPs are provided in Table 2.
