COMT and schizophrenia: Conversely, in nine genetic polymorphisms tested across genes coding for seven proteins related to noradrenergic receptors or NE synthesis or metabolism (ADRA1A, ADRA2A, ADRA2C, ADRB3, DBH, MAOA, and COMT), no association with AP-induced weight gain in patients with schizophrenia was identified (51).