AIM: We investigated the association of electroconvulsive therapy (ECT) with anxiolytic and sleep medication use in patients with major depressive disorder (MDD) and schizophrenia (SZ). METHODS: This nationwide observational study analyzed data from 3,483 MDD inpatients and 6,663 SZ inpatients. Patients with MDD and SZ were classified into those who underwent ECT during hospitalization and those who did not. A propensity score-matching method was performed to adjust for preadmission characteristics and clinical information, which were expected bias between the two groups. Rates of anxiolytic and sleep medication use at discharge were compared in the matched sample. RESULTS: 500 MDD patients were assigned to both groups. In the matched MDD sample, the rate of anxiolytic and sleep medication use at discharge was significantly lower in the ECT group than in the non-ECT group (64.9% vs 75.8%, p=1.7×10-4 ). In the ECT group, the rate of anxiolytic and sleep medication use at discharge was significantly lower than that prior to admission (64.9% vs 73.2%, p=1.2×10-14 ). 390 SZ patients were allocated. In the matched SZ sample, the ECT group was not significantly different from the non-ECT group in the rate of anxiolytics and sleep medications use at discharge (61.3% vs 68.2%, p=4.3×10-2 ). In the ECT group, the rate of anxiolytics and sleep medications use at discharge was significantly lower than that before admission (61.3% vs 70.5%, p=4.4×10-4 ), although this was not the primary outcome. CONCLUSION: Reduction of anxiolytic and sleep medication use may be considered positively when ECT is indicated for treatment of MDD. This article is protected by copyright. All rights reserved.