These findings corroborate and strengthen certain previous reports. Rs578776 (CHRNA3) has been previously associated with nicotine dependence in subjects of European ancestry [Saccone et al., 2009a, 2009b, 2010b; Weiss et al., 2008] and heavy smoking [Stevens et al., 2008] with the minor allele (T) acting in a protective manner against nicotine dependence. Our results also support the protective effect of the minor allele where a positive beta (0.02) indicated a later age of first regular smoking among individuals with 1 or 2 copies of the T allele. However, the SNP is not known to be functional, so the basis for the association needs to be investigated further. SNP rs1948 (CHRNB4) has previously been associated with tobacco and alcohol age of initiation in the CADD sample and NYS-FS samples [Schlaepfer et al., 2008], but few other studies have focused on this locus. SNP rs1948 was recently associated with the tolerance factor of the Nicotine Dependence Syndrome Scale (NDSS) (P = 0.0071) [Broms et al., 2012] and SNP rs684513 (major allele) has been previously associated with nicotine dependence [Winterer et al., 2010]
