The aims of the study were (1) to investigate the prevalence of abnormally low PRL after switching to aripiprazole in patients with schizophrenia, (2) to evaluate whether such an abnormally low PRL was associated with rebound in psychotic symptoms, and (3) to evaluate the concurrency of both the trend of cumulated proportion of abnormally low PRL and the trend of cumulated proportion of rebound in psychotic symptoms during the trial. Here, PRL is linked to schizophrenia.