Effectiveness of medical fee revisions for psychotropic polypharmacy in patients with mood disorders in Japan: An interrupted time-series analysis using a nationwide inpatient database

Background: This study aimed to evaluate the effects of medical fee revisions aimed to reduce psychotropic polypharmacy in Japan on the proportion of psychotropic polypharmacy in discharge prescriptions for patients with major depressive disorder (MDD) or bipolar disorder (BD) using a nationwide inpatient database. Methods: In this retrospective cohort study, we used the Diagnosis Procedure Combination database to identify patients with MDD or BD discharged between April 2012 and March 2021. We targeted medical fee revisions in October 2014, April 2016, and April 2018. The major outcome was the monthly proportion of psychotropic polypharmacy in prescription at discharge using the criteria following the April 2018 revision (antidepressants ≥3, antipsychotics ≥3, anxiolytics ≥3, hypnotics ≥3, or sum of anxiolytics and hypnotics ≥4). We performed interrupted time series analyses to evaluate the changes in level and trend between pre- and post-revisions. Results: We identified 63,289 and 33,780 patients with MDD and BD respectively in the entire study period. In both the patient groups, there were significant decreases in the proportion of psychotropic polypharmacy at revision in October 2014, and no significant trend and level change at revision were observed in April 2016 and April 2018, with a few exceptions. Conclusions: The medical fee revisions aimed to reduce psychotropic polypharmacy in Japan might have had a limited impact on discharge prescriptions for patients with MDD and BD.