We now report “nontemplate” GWA [24] studies that compare allele frequencies for almost 870,000 autosomal SNPs in each of two independent samples (one European-American and the second African-American) of controls vs polysubstance abusers who report heavy use and dependence on at least one illegal substance. We have characterized and collected these case and control samples at a single site. We use a nontemplate GWA approach with DNA pooling to study the genetics of this illegal behavior. We analyze genes that are identified by “replicated” results from these data in each of two ways that appear to complement each other (though they are not independent of each other): 1) “converge then cluster”, based on identification of SNPs within a gene that a) display nominally significant case vs control allele frequency differences in each of these two samples and b) lie near other SNPs with the same properties, and 2) “cluster then converge”, based on SNPs within genes that are identified in each of the two samples by clusters of SNPs that a) display nominally significant case vs control allele frequency differences
