OPRD1 and attention deficit-hyperactivity disorder: Several previously postulated psychiatric risk genes from candidate studies were revealed in these constructs, including neural cell adhesion molecule 1 (NCAM1) which was significant in the schizophrenia and BIP model33,34 and the Delta opioid receptor gene OPRD1 which survived correction in the schizophrenia meta-analyses with ADHD and MDD, respectively35,36.