SNP rs1948 was chosen due to a previously established association with AOI [Schlaepfer et al., 2008]. Based on previous results [Saccone et al., 2010a; Saccone et al., 2009a], we also included three statistically distinct nicotine dependence loci in the CHRNA5/A3/B4 gene cluster: rs16969968, rs578776, and rs588765. If a group did not have genotype data for SNPs rs16969968, rs578776, or rs588765 we chose a highly correlated (r2 > 0.8) SNP proxy. Another option would have been to use imputed data. However, in that situation, it would have been important for all imputation to be performed consistently between groups which would have required some groups to reimpute specifically for this project. The advantage of using an imputed SNP instead of a high-LD proxy for this study was not compelling because the imputation quality of the SNP would need to be taken into account as well. Thus, imputed SNPs were unlikely to add a significant amount of information to this study and/or change the take home message. SNP proxies for applicable datasets are shown in Table 2. Information on r2 was obtained using
