It has been found that the C957T polymorphism (SNP: rs1799732), located in exon 7 of DRD2 (gene map locus 11q23), alters the availability of DRD2 and that a higher frequency of the CC genotype is associated with a higher risk of alcoholism [10,11], nicotine dependence [12], and cannabis dependence [13]. This evidence concerns the gene DRD2 and nicotine dependence.