detected in populations of European descent will not necessarily have the same impact in populations of African descent. For example, if the causal variant is less common in populations of African descent, it may play less of a role in the genetic etiology of substance use outcomes in individuals with that ancestral background; conversely, there may be more common alleles that impact substance use outcomes in individuals of African descent that are not as common in populations of European descent, and therefore, would not be detected without explicit study of individuals of African ancestry. Finally, lower linkage disequilibrium also means that more genetic markers are needed to adequately cover genetic variation across the genome in populations of African descent for gene identification efforts. Thus, most standard genotyping platforms provide less thorough coverage of genetic variation among populations of African descent, thereby decreasing the likelihood of detecting relevant associated variants in this population.41,43,44
