The allelic and genotypic association of SNPs with opioid and cocaine dependence were determined using the Fishers, Chi-square tests and model tests in the software package PLINK v1.04 (Purcell et al., 2007). Logistic regression analyses were also performed using PLINK, using ethnicity (EA/AA) as a covariate in the regression model. All p-values generated from these analyses were corrected for multiple comparisons using the false discovery rate (FDR) procedure (Benjamini et al., 2001).
