Title: Green environment and incident depression in South Africa: a geospatial analysis and mental health implications in a resource-limited setting
Authors: Tomita A, Vandormael AM, Cuadros D, Di Minin E, Heikinheimo V, Tanser F, Slotow R, Burns JK.
Journal: Lancet Planetary Health,1:152?62 (2017)
Background Unprecedented levels of habitat transformation and rapid urbanisation are changing the way individuals interrelate with the natural environment in developing countries with high economic disparities. Although the potential bene t of green environments for mental health has been recognised, population-level evidence to this e ect is scarce. We investigated the e ect of green living environment in potentially countering incident depression in a nationally representative survey in South Africa.
Methods We used panel data from the South African National Income Dynamics Study (SA-NIDS). Our study used SA-NIDS data from three waves: wave 1 (2008), wave 2 (2010), and wave 3 (2012). Households were sampled on the basis of a strati ed two-stage cluster design. In the rst stage, 400 primary sampling units were selected for inclusion. In the second stage, two clusters of 12 dwelling units each were drawn from within each primary sampling unit (or 24 dwelling units per unit). Household and individual adult questionnaires were administered to participants. The main outcome, incident depression (ie, incident cohort of 11 156 study participants without signi cant depression symptoms at their rst entry into SA-NIDS), was assessed in the adult survey via a ten item version of the Center for Epidemiologic Studies Depression Scale; a total score of ten or higher was used as a cuto to indicate signi cant depressive symptoms. Each participant was assigned a value for green living space via a satellite-derived normalised di erence vegetation index (NDVI) based on the GPS coordinates of their household location.
Findings Overall, we found uneven bene t of NDVI on incident depression among our study participants. Although the green living environment showed limited bene t across the study population as a whole, our nal analysis based on logistic regression models showed that higher NDVI was a predictor of lower incident depression among middle- income compared with low-income participants (adjusted odds ratio [aOR] 0.98, 0.97?0.99, p<0.0001), although when this analysis was broken down by race, its positive e ect was particularly evident amongst African individuals. Living in rural areas was linked to lower odds of incident depression (aOR 0.71, 0.55?0.92, p=0.011) compared with study participants residing in urban informal areas that often lack formal planning.
Interpretation Our results imply the importance of green environments for mental wellbeing in sub-Saharan African settings experiencing rapid urbanisation, economic and epidemiological transition, rea rming the need to incorporate environmental services and bene ts for sustainable socioeconomic development.
Funding South African Medical Research Council, National Institutes of Health, and Academy of Finland.
Citation: Tomita A, Vandormael AM, Cuadros D, Di Minin E, Heikinheimo V, Tanser F, Slotow R, Burns JK. Green environment and incident depression in South Africa: a geospatial analysis and mental health implications in a resource-limited setting Lancet Planetary Health,1:152?62 (2017).