BACKGROUND: During the COVID-19 pandemic, reports from several European mental health care systems hinted at important changes in utilization. So far, no study examined changes in utilization in the German mental health care inpatient and outpatient mental health care system comprehensively.

METHODS: This longitudinal observational study used claims data from two major German statutory health insurances, AOK PLUS and BKK, covering 162,905 inpatients and 2,131,186 outpatients with mental disorders nationwide. We analyzed changes in inpatient and outpatient mental health service utilization over the course of the first two lockdown phases (LDPs) of the pandemic in 2020 compared to a pre-COVID-19 reference period dating from March 2019 to February 2020 using a time series forecast model.

RESULTS: We observed significant decreases in the number of inpatient hospital admissions by 24-28% compared to the reference period. Day clinic admissions were even further reduced by 44-61%. Length of stay was significantly decreased for day clinic care but not for inpatient care. In the outpatient sector, the data showed a significant reduction in the number of incident outpatient diagnoses.

CONCLUSION: Indirect evidence regarding the consequences of the reductions in both the inpatient and outpatient sector of care described in this study is ambiguous and direct evidence on treatment outcomes and quality of trans-sectoral mental healthcare is sparse. In line with WHO and OECD we propose a comprehensive mental health system surveillance to prepare for a better oversight and thereby a better resilience during future global major disruptions.