COMT and attention deficit-hyperactivity disorder: To our knowledge, COMT is chiefly produced by nerve cells in the brain and its variants were found to be associated with risk for mental illness and schizophrenia, other disorders that affect thought (cognition), emotion, bipolar disorder, panic disorder, anxiety, obsessive-compulsive disorder (OCD), eating disorders, and attention deficit hyperactivity disorder (ADHD) (disease http://ghr.nlm.nih.gov/gene/COMT).