The candidate gene approach is limited in scope, but this study suggests that testing biological candidate genes in a well-characterized population with a well-defined phenotype may facilitate the identification of genetic variants that are associated with vulnerability to develop heroin addiction and are specific to an ethnic group. This approach is more economical than whole-genome screening and may increase the power of the study due to the smaller number of tests performed. We cannot determine if the negative findings in this study indicate true negative association, because the SNP coverage of some of the genes may be limited and due to the limited power of the study.
