In addition to the CHRNA5–CHRNA3–CHRNB4 locus, GWAS have identified, in distinct genomic locations, several SNPs in CHRNAB3–CHRNA6, EGLN2–CYP2A6 and LOC100188947 reaching genome-wide significance for association with CPD47,58. CHRNB3, CHRNA6 and CYP2A6 have been widely studied as candidates for smoking and nicotine dependence, and the results seem convincing. One of these same studies47 also identified brain-derived neurotrophic factor (BDNF) as a candidate gene for smoking initiation.
