Hospitalizations for mental disorders among public assistance recipients and the general population in Japan: A repeated cross-sectional study using national government statistics

Background In Japan, hospital stays for patients with mental disorders are longer than those in many countries, leading to employment difficulties and reliance on public assistance. Mental disorders are common among public assistance recipients (PARs), but category-specific differences in hospitalization rates relative to the general population remain unclear. Using national government statistics, we compared hospitalization rates by subcategories of mental disorder between PARs and the general population, and assessed age-standardized differences to inform mental health policies. Methods We conducted a repeated cross-sectional study using data obtained from national government statistics for 2014, 2017, 2020, and 2023. We compared hospitalization rates (H-rates; inpatients per 100000 on a given day) for mental disorders between PARs and the general population. Diagnoses followed the International Classification of Diseases, Tenth Edition (ICD-10), focusing on “V Mental and behavioural disorders” and its three subcategories (defined for this study): V-1 Schizophrenia disorders, V-2 Mood disorders, and V-3 Neurotic disorders. We calculated crude hospitalization ratios (CHRs; PARs/general population H-rate) and standardized hospitalization ratios (SHR) using indirect age adjustments with 95% confidence intervals (CIs). Results From 2014 to 2023, both PARs and the total population declined. By 2023, PARs and the total population were about 2.0 and 124.4 million, with 52.6% and 29.1% aged ≥ 65, respectively. Across the subcategories, H-rates were consistently higher in PARs than in the general population and were the highest for V-1 Schizophrenia disorders. H-rates declined overall, with smaller decreases for V-2 Mood and V-3 Neurotic disorders. Regarding SHRs, men generally exceeded women, whereas for V-1 the sex difference was minimal across the years. Across the survey years, SHRs for all subcategories exceeded 1 and surpassed those for “All diseases”; the highest by sex were V-3 in men and V-1 in women. Conclusions Among PARs, H-rates were higher than those in the general population not only for V-1 but also for V-2 and V-3. In the SHR trends, the decline in V-1 likely reflected an apparent improvement due to fewer older PARs, with no clear improvement in V-2 or V-3. Policies should move beyond V-1 emphasis and strengthen post-discharge and employment-transition support.