SLC6A3 and attention deficit-hyperactivity disorder: The DAT Val559 variant, identified in ADHD [14], ASD [16], and BPD [15], is associated with aberrant, transporter-mediated DA efflux in transfected cells [17] with alterations in presynaptic control of DA release and clearance and behavior, as well as basal and drug modulated behaviors, evident in vivo [19, 21, 22].