In an association and family study, Franke et al. [77] failed to find an association between the silent rs2234918 mutation and heroin or alcohol dependence. This study included 233 heroin-dependent subjects, 262 alcohol dependent subjects, and 173 controls, all of German origin, as well as the biological parents of 90 heroin dependent subjects and 72 alcohol dependent subjects [77]. Despite the similar ethnic background of the samples selected for these studies [76, 77], the allele and genotype frequencies of individuals with heroin and alcohol dependence compared to controls were not found to be statistically significant [77]. In addition, there was no preferential transmission of alleles in families of subjects with heroin or alcohol dependence [77].
