yin-yang haplotypes and alcohol dependence or drug dependence unlike the many earlier studies in Caucasians (12–21). The two previously reported studies in African Americans showed no association between the yin-yang haplotypes and alcohol dependence (22) or polysubstance abuse (23). Moreover, a recent, dense genomewide linkage scan for alcohol dependence in African Americans did not find a linkage peak at the GABAA receptor gene complex on chromosome 4 (45), unlike earlier studies in Caucasians (46) and Native Americans (47).
