ANKK1 and familial hyperprolactinemia: The results of this study indicate that the prevalence of antipsychotic‐induced HPRL in Russian patients with schizophrenia is higher in carriers of rs2734849*С allele of ANKK1 gene whereas allele rs2734849*T of ANKK1 gene has a protective effect against antipsychotic‐induced HPRL in this sample.