Many studies have extensively investigated the role of polymorphisms in the DR2 gene (DRD2), e.g., Taq1A (rs1800497), C957T (rs6277), and −141Cins/del (rs1799732), in neuropsychiatric disorders such as schizophrenia, alcoholism, Parkinson’s disease, substance addiction, and ADHD [33,34,35,36,37,38]. Here, DRD2 is linked to attention deficit-hyperactivity disorder.