CHRNA4 and nicotine dependence: In our European-American population, we did not find evidence of significant associations (P<0.05 in early or late onset smokers) among the four CHRNA4 SNPs in common with our study (rs2273504, rs2236196, rs1044396, rs1044397; Table S3) and previous candidate gene association studies of nicotine dependence in Chinese men [5], and females of European-American and African-American descent [6].