Our findings of higher SNP heritability for nicotine dependence (as measured by FTND) relative to other smoking phenotypes is consistent with observations of differential GWAS associations for different smoking phenotypes (Chen et al., 2012; Hancock et al., 2015; Rice et al., 2012). For example, variants in the CHRNA6/CHRNB3 region are more strongly associated with FTND-based nicotine dependence than CPD (Rice et al., 2012). In contrast, FTND-based nicotine dependence and CPD were equally associated with genetic variants in the CHRNA5/CHRNA3/CHRNB4 region (Chen et al., 2012). This highlights the complexity of the relationship between smoking behavior and genetics.
