We performed a sex-stratified (Cochran-Mantel-Haenszel test) initial association analysis on 1536 LD-tagging SNPs in 106 candidate system genes in an EA sample that included 359 male subjects affected with a DUD, 138 male control subjects, 39 female subjects affected with a DUD, and 221 female control subjects. Gene-wise significance was calculated using Fisher's approach to combining p values across the gene. To account for dependence between the SNPs, a null distribution of Fisher's combined p values (25) was constructed by permuting case-control status 1 million times. Significance of the actual p values was assessed against the distribution of permuted p values.
