COMT and attention deficit-hyperactivity disorder: The study aimed at assessing whether children with ADHD, with or without FASD, differ in terms of catechol-O-methyltransferase (COMT, rs4680) and dopamine receptor D2 (DRD2, rs1076560 rs1800497) gene polymorphisms, and if the genetic predisposition affects the response and safety of the methylphenidate (MPH) treatment in children with ADHD and high prenatal alcohol exposure (hPAE) with or without morphological features FASD, according to the Washington Questionnaire.