For rs1044394, one other study has provided evidence of an association with ND as measured both by DSM-IV ND criteria and the Fagerström Test for ND (Han et al, 2011). In contrast to our results where the minor allele was associated with increased risk of ND symptoms, Han et al. found evidence that the minor allele lowered the risk of ND (Han et al. 2011). Differences do exist between these studies that could account for the difference in effect. The Han et al. study examined both African Americans and EA, while we examined non-Hispanic EA and self-identified Hispanics. The association with rs1044394 and ND was driven by the African American sample in their study (although there was suggestive evidence in the EA sample). It is also possible that the differences observed between these studies are due to differences in rare functional variants associated with rs1044294 that differ between our samples. There is evidence that CHRN SNPs show opposite allelic effects with different drugs (Grucza et al. 2008; Sherva et al. 2010; Wang et al. 2008) and in some cases the
