were unable to compare the results of the current limited-scope investigation to the results of a potential multiple system or genome-wide scoring approach with regard to genetic influences on cocaine dependence. (To our knowledge there is currently no published GWAS of cocaine dependence in the existing literature on which we might be able to base a genome-wide scoring model.) Nevertheless, the substantial heritability of cocaine dependence suggests that there likely exist numerous influential genetic variants whose effects on cocaine dependence could be discovered using genome-wide approaches, given the availability of an adequately powered sample or meta-analysis. Further, the reliance of the current study on genotypes selected from existing genome-wide data necessarily limited our ability to include non-SNP variation (e.g., the frequently-investigated 48bp VNTR in DRD4, Munafò et al. 2008). Thus, there may remain phenotypic variance attributable to non-SNP polymorphisms within these dopaminergic genes that was unmodeled in our current analysis.
