The effect of the DAT1 gene on striatal volumes may help explain smaller volumes of caudate nucleus and putamen typically found in children with ADHD (Ellison-Wright et al. 2008; Frodl and Skokauskas 2012; Nakao et al. 2011; Valera et al. 2007). This evidence concerns the gene SLC6A3 and attention deficit-hyperactivity disorder.