with the broader epidemiological literature3,21. For instance, AA are more likely to initiate use of cannabis prior to alcohol and are more likely to escalate to problem use60,61. Similarly, AA are at nearly 3.5 increased odds of transitioning from cocaine use to dependence than their EA counterparts, even after adjustment for sociodemographic features and psychiatric comorbidity62. However, these population differences may reflect socio-cultural trends or represent barriers to access to prevention programs among minority populations, thus increasing rates of lifetime drug dependence63. While we might speculate that the three loci identified in the AA GWAS are more likely to relate to liability to both alcohol and drug dependence, this observation may merely be an artifact of cultural effects on the expression of genetic susceptibility.
