2010). This polymorphism in the hDAT gene has been consistently associated with cessation of smoking, obesity in smokers, ADHD, schizophrenia, and alcoholism (Heinz and Goldman 2000). Imaging studies have suggested that this genetic variation might affect the availability of DAT in the striatum of human subjects (van Dyck et al. 2005). Overexpression of variant hDAT constructs in cell lines suggests that the 9‐ or 10‐repeat VNTR can regulate dopamine transporter density (VanNess et al. 2005), but such studies are limited since they lack the proper cellular milieu. This evidence concerns the gene SLC6A3 and attention deficit-hyperactivity disorder.