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Aims Studies have shown association between common variants in the alpha 6-beta 3 nicotinic receptor subunit gene cluster and nicotine dependence in European ancestry populations. We investigate whether this generalizes to African Americans, whether the association is specific to nicotine dependence and whether this region contains additional genetic contributors to nicotine dependence. Design We examined consistency of association across studies and race between the alpha 6 beta 3 nicotinic receptor subunit locus and nicotine, alcohol, marijuana and cocaine dependence in three independent studies. Setting United States of America. Participants European Americans and African Americans from three case-control studies of substance dependence. Measurements Subjects were evaluated using the Semi-Structured Assessment for the Genetics of Alcoholism. Nicotine dependence was determined using the Fagerstrom Test for Nicotine Dependence. Findings The single nucleotide polymorphism rs13273442 was associated significantly with nicotine dependence across all three studies in both ancestry groups [odds ratio (OR) = 0.75, P = 5.8 x 10(-4) European Americans; OR = 0.80, P = 0.05 African Americans]. No other substance dependence was associated consistently with this variant in either group. Another SNP in the region, rs4952, remains modestly associated with nicotine dependence in the combined data after conditioning on rs13273442. Conclusions The common variant rs13273442 in the CHRNB3-CHNRA6 region is associated significantly with nicotine dependence in European Americans and African Americans across studies recruited for nicotine, alcohol and cocaine dependence. Although these data are modestly powered for other substances, our results provide no evidence that correlates of rs13273442 represent a general substance dependence liability. Additional variants probably account for some of the association of this region to nicotine dependence
