Finally, three genes or gene regions, i.e., GABRA2, CHRNA6-CHRNB3 and CHRNA5-CHRNA3-CHRNB4 that have previously been associated to both alcohol and nicotine dependence [Bierut et al., 2007; Edenberg et al., 2004; Liu et al., 2010; Ray et al., 2009; Saccone et al., 2007; Thorgeirsson et al., 2010] were also explored in the present study. They were only nominally associated with alcohol and nicotine co-dependence (Table S6); they were neither replicable between EAs and AAs, genome-wide significant, nor on the top-ranked gene list in the present study (Table S3), consistent with previous results using the same SAGE dataset [Bierut et al., 2010; Wang et al., 2011].
