DRD2 and cocaine dependence: These risk factors were positively (p < 10−3) correlated to A1 allelic prevalence, showing a strong association to the minor alleles (A1 and B1) of the dopamine receptor D2 gene (DRD2) with cocaine addiction suggesting that a gene located on the q22–q23 region of chromosome 11 confers susceptibility to cocaine addiction [21].