HCRTR2 and attention deficit-hyperactivity disorder: The coding regions of the orexin-1/hypocretin-1 (OX1R) receptor gene, the orexin-2/hypocretin-2 (OX2R) gene, and the prepro-orexin gene were examined in patients with Excessive Daytime Sleepiness, TD, or ADHD and healthy controls (162).