The risk of developing nicotine addiction has been associated with genetic variations in genes that encode for nAChRs, particularly those located in the chromosomal region 15q25 (CHRNA5-CHRNA3-CHRNB4 gene cluster) [42], in chromosome 8 (CHRNB3–CHRNA6 gene cluster) [70], and in CHRNA2 [71]. This evidence concerns the gene CHRNA2 and nicotine dependence.