Healthcare utilization and medical costs among adults with selected psychiatric disorders: a nationwide retrospective cohort study

We examined whether documented selected psychiatric disorders in 2021 were associated with healthcare utilization and medical costs during 2022 using nationwide population-based data from South Korea. We conducted a retrospective cohort study using the National Health Insurance Service database. Adults aged ≥ 18 years were classified according to the presence or absence of at least one documented diagnosis of 10 selected psychiatric disorders during 2021; all covariates were also assessed in 2021. Outcomes during 2022 included any emergency department (ED) visit, psychiatric-related ED visit, hospitalization, psychiatric-related hospitalization, and total medical costs. After 1:1 propensity score matching, 567,884 individuals were included (283,942 per group). Binary outcomes were analyzed using modified Poisson generalized linear models with robust standard errors, and medical costs using a gamma model with a log link. In the matched cohort, adults with documented psychiatric disorders had higher risks of any ED visit (11.9% vs. 8.6%; risk ratio [RR], 1.38; 95% confidence interval [CI], 1.35–1.41), psychiatric-related ED visit (0.1% vs. < 0.1%; RR, 43.85; 95% CI, 23.43–82.08), any hospitalization (8.8% vs. 4.4%; RR, 2.01; 95% CI, 1.93–2.10), and psychiatric-related hospitalization (0.6% vs. < 0.1%; RR, 40.92; 95% CI, 32.45–51.60). Mean annual medical costs were also higher (USD 620.6 vs. USD 296.8; cost ratio, 2.09; 95% CI, 2.04–2.13; all P < 0.001). Documented diagnoses of selected psychiatric disorders in 2021 were associated with higher subsequent risks of ED visits and hospitalizations and greater medical costs during 2022. These findings support coordinated care addressing both psychiatric and physical health needs.