Greenness and Depressive Symptoms of 7 Major Cities in Korea

Abstract

Background/Aim: Greenness is expected to affect mental health through stress reduction, cognitive restoration, increased physical activity, increased social interaction, noise mitigation. Some studies have suggested the association between greenness and mental health, however, evidence remains limited. The objective of this study is to examine the association between greenness and depressive symptoms in 7 major cities of Korea. Methods: This study included a total of 64,909 individuals from Community Health Survey 2009. Individuals with Center for Epidemiological Studies Depression (CES-D) score ≥ 16 were classified as having depressive symptoms. District-level of greenness was measured by Normalized Difference Vegetation Index (NDVI). Logistic regression was used to analyse the association between greenness and depressive symptoms. Results: Compared to the lowest quartile (1st quartile), odds ratio (OR) of having depressive symptoms was 0.795 (95% confidence interval (CI): 0.730, 0.867) in the highest quartile of NDVI (4th quartile), 0.870 (95% CI: 0.804, 0.941) in the 3rd quartile and 0.805 (95% CI: 0.748, 0.867) in the 2nd quartile. When NDVI was treated as continuous variable, OR of having depressive symptoms was 0.859 (95%CI: 0.820, 0.900) with an interquartile range (17.61) increase of NDVI. Conclusions: This study showed that a lower greenness level was associated with depressive symptoms in 7 major cities of Korea. Further studies are needed to understand the effect of greenness on mental health.