Human association studies have found associations between DRD2 and cannabis use. Conner et al [113] found that boys carrying one copy of the TaqA1 allele experienced their first cannabis-related ‘high’ at an earlier age than those who did not have this allele. Sakai et al [114] have also shown the TaqA1 allele to be associated with adolescent alcoholism. Since 93% of their alcohol dependent adolescents also reported comorbid cannabis abuse/dependence this sample may have identified an influence of Taq1A on comorbid alcohol and cannabis dependence. It is noteworthy that the TaqA1 polymorphism has recently been mapped to exon 8 of a neighboring gene ANKK1 (ankyrin repeat and kinas domain containing 1)[115]. Therefore, it remains to be seen whether prior associations with DRD2 are attributable to ANKK1.
