Although dependence is common in all populations, to date all of large-scale GWAS have been performed in populations of European descent. Though the underlying biological mechanisms that lead to the development of substance dependence are most likely the same across populations, varying allele frequencies can alter the relative importance of specific genetic risk factors in different populations. For example, the variant rs16969968, which is relatively frequent in populations of European descent (37% allele frequency), is rare in populations of African or Asian descent (0% to 3% allele frequency) (Bierut et al., 2008). Similarly, the polymorphisms that cause amino acid changes in alcohol metabolizing genes, rs671 and rs1229984, are common in Asian populations, but are rare in populations of European and African descent (Edenberg et al., 2007). Thus, rs16969968 will play a larger role in the development of heavy smoking and nicotine dependence in populations of European ancestry compared to populations of African and Asian ancestry. Similarly, rs671 and rs1229984 will more strongly influence alcohol consumption and alcohol dependence in Asian populations compared to European and African populations. A new genetic
