We detected four SNPs that in aggregate accounted for 0.55% of testing sample variance in cocaine dependence symptoms. These four SNPs were individually nominally significant in the training sample, but none were significant in the testing sample (p=0.14-0.59). The effects of these SNPs in the testing sample were nominally significant only when considered in the aggregate, and replication of this effect is necessary before it may be considered reliable. Rather than imply that the effects of these SNPs are of primary importance in identifying individuals who are at increased risk of cocaine dependence, we endeavored to illustrate the potential utility of such an aggregate SNP approach to studying the influence of measured genotypes on behavioral or psychiatric phenotypes, for which large datasets are unavailable (making genome-wide association and scoring approaches likely substantially underpowered) and for which a reasonable body of research and/or theoretical literature exists to allow for the a priori selection of a pathway for inclusion in the construction of a targeted scoring approach. The current findings demonstrate that such a candidate system scoring approach may be potentially useful
