DRD4 and attention deficit-hyperactivity disorder: As mentioned above, the overexpression of GIT1 disrupts the internalization of numerous G protein‐coupled receptors (Claing et al., 2000; Hoefen & Berk, 2006; Premont et al., 1998), including dopamine receptors; this may be the mechanism underlying the GIT1 × DRD4 effects on impulsivity and response time variability in ADHD patients observed in this study.