CHRNA5 and drug dependence: Although no significant interactions of CA and genotypes of CHRNA5 rs16969968 on CHRNA5 cg17108064 methylation were observed, we cannot exclude the possibility that CA-induced methylation changes in the CHRNA5 promoter region and the minor (A) allele of the functional CHRNA5 SNP rs16969968 may play a concerted role in increasing risk for alcohol or drug dependence.