The aim of this study, which was based on SDs in schizophrenia and bipolar disorder patient groups under pharmacotherapy, was to investigate the relationship between SD and genetic polymorphisms (eNos, nNos, DRD2-141CIns/Del, DRD2Taq1A polymorphism), prolactin levels, and diseases to shed light on the use of drugs, diseases, genetics, and individual factors as predictors of sexual side effects in patients receiving pharmacotherapy. This evidence concerns the gene PRL and bipolar disorder.