DRD4 and attention deficit-hyperactivity disorder: In summary, our findings suggest that variants in DRD4, ADGLR3 and FGF1 are associated with ADHD endophenotypes related to perceptual organization and, as such, may constitute a new explanatory view of ADHD considering that people with the disorder present alterations in visual and speech perception, which are also determinants of symptom severity [116].