Lower suicidal ideation linked to easier access to urban green spaces during the COVID-19 pandemic: A nationwide study in Japan

Urban green spaces (UGSs) have been linked to improved mental health and lower suicide rates, yet their protective role during large-scale crises remains underexplored. We examined associations of UGS accessibility with long-term and pandemic induced new-onset suicidal ideation during the early phase of the COVID-19 pandemic in urban Japan, using data from a nationwide health survey of 17,376 participants (August 2020). Modified Poisson regression models estimated prevalence ratios (PRs) for suicidal ideation by UGS accessibility (area, number, and type) within 5, 10, and 15-minute walking thresholds from home, controlling for individual and area-level confounders. UGS accessibility exhibited dose-response relationships with clear distance-dependency patterns. Within 5-minute walking distance, larger UGSs (>2 ha) were associated with 67 % lower prevalence of new-onset suicidal ideation (PR = 0.330, p = 0.010), while medium-sized areas (0.25–2 ha) showed 46 % lower prevalence (PR = 0.539, p = 0.001). Long-term suicidal ideation showed similar but attenuated associations. Having access to two UGSs showed the strongest associations. These associations diminished at 10-minute distances and were not significant at 15-minute thresholds. Among UGS types, neighbourhood parks (PR = 0.641, p = 0.005) and buffer greenspaces/greenways (PR = 0.526, p = 0.089) showed significant associations with lower prevalence of new-onset ideation at the 5-minute threshold. Community parks showed associations primarily at longer distances (10 and 15 min). When stratified by income, the association was strongest among middle-income populations, with limited associations observed in low-income groups, potentially due to reduced access during the pandemic. This nationwide analysis underscores the importance of incorporating accessible green infrastructure into urban mental health resilience planning during public health emergencies.