COMT and schizophrenia: These included the dopamine D5 microsatellite marker (DRD5), linked in some studies to attention deficit [33,34], the insulin-like growth factor 2 (IGF2, three single nucleotide polymorphisms), linked to eating disorders and self-report measures of altruism [15,35], catechol-O-methyltransferase (COMT) [36], linked to cognitive function and schizophrenia [37], and monoamine oxidase A (MAOA) [38], linked to violence [39].