DRD2 and schizophrenia: Dolzan et al.4 investigated the effects of DRD1 A-48G, DRD2 Ins -141C Del, and DRD2 Ser 311 Cys variants on medical treatments of schizophrenia by risperidone, haloperidol, fluphenazine, or zuclopenthixole, and found no variations in the treatment response or the incidence of adverse effects.