Rigorous studies of DRD1 (5q35.1) and AD have typically estimated positive associations with modest effect sizes (Batel et al., 2008; Kim et al., 2007), while reports examining this phenotype and DRD3 (3q13.3) have been negative (Le Foll et al., 2009). A recent review supports an association between the 48-bp variable number of tandem repeats (VNTR) in DRD4 (11p15.5) and an intermediate phenotype termed urge for addictive substances, which refers to craving for substances of abuse (McGeary, 2009). We know of no rigorous reports investigating associations between DRD5 (4p16.1) and AD or related traits.
