Association between greenness and suicide attempts in patients with depression: A nationwide longitudinal cohort...

Although multiple emerging studies have suggested the relationship between greenness and mental health, evidence regarding associations among green space, suicide attempts, and depression is still limited. In this study, we aimed to estimate the association of greenness with suicide attempts in patients with depression.

This study used the National Health Insurance Service database in South Korea to construct a cohort of patients diagnosed with depression during 2012-2013 (n = 677,498) with an 8-year follow-up period. Residential greenness was measured as the district-level annual average of the Enhanced Vegetation Index. The primary outcome was the suicide attempt, and categorized suicide attempts (non-violent and violent methods) were also examined. A Cox regression with time-varying variables was performed to assess the association between greenness and suicide attempts, and stratified analyses were conducted by sex, age, insurance premium, and disability status.

A higher level of greenness was associated with lower suicide attempts among patients with depression (HR: 0.789; 95% CI: 0.677, 0.918). The protective association was higher for suicide attempts by violent methods (HR: 0.733; 0.545, 0.987) than non-violent methods (HR: 0.812; 0.680, 0.970), based on point estimates. Among patients with depression, males, individuals aged 35-64 years, and Medical Aid beneficiaries showed a more prominent association with greenness.

This nationwide cohort study provides epidemiological evidence for the benefits of residential greenness in reducing suicide among patients with depression and suggests the appropriateness of public health policies for increasing green spaces.