Access to green space, physical activity and mental health: a twin study

Abstract

Background Increasing global urbanisation has resulted in a greater proportion of the world’s population becoming exposed to risk factors unique to urban areas, and understanding these effects on public health is essential. The aim of this study was to examine the association between access to green space and mental health among adult twin pairs. Methods We used a multilevel random intercept model of same-sex twin pairs (4338 individuals) from the community-based University of Washington Twin Registry to analyse the association between access to green space, as measured by the Normalised Difference Vegetation Index and self-reported depression, stress, and anxiety. The main parameter of interest was the within-pair effect for identical (monozygotic, MZ) twins because it was not subject to confounding by genetic or shared childhood environment factors. Models were adjusted for income, physical activity, neighbourhood deprivation and population density. Results When treating twins as individuals and not as members of a twin pair, green space was significantly inversely associated with each mental health outcome. The association with depression remained significant in the within-pair MZ univariate and adjusted models; however, there was no within-pair MZ effect for stress or anxiety among the models adjusted for income and physical activity. Conclusions These results suggest that greater access to green space is associated with less depression, but provide less evidence for effects on stress or anxiety. Understanding the mechanisms linking neighbourhood characteristics to mental health has important public health implications. Future studies should combine twin designs and longitudinal data to strengthen causal inference.

The Physical Activity and Redesigned Community Spaces (PARCS) Study: Protocol of a natural experiment to investigate the impact of citywide park redesign and renovation

“…However, two other studies showed null findings [60, 61]. Similarly, while some research has shown a significant inverse association of exposure to neighborhood green space with multiple aspects of mental ill-health, such as depression, anxiety and stress [62], other research has found this association to be limited only to some but not other aspects of mental health [63]. Of note, the effect of parks on mental health may be more pronounced in low-income neighborhoods.…”

The effects of air pollution on individual psychological distress

“…In particular, in areas with higher levels of air pollution, people tend to reduce the amount of time they spend outdoors 12 . Such averting behavior introduces a number of indirect pathways through which air pollution may further induce or worsen psychological distress, including limited exposure to sunlight and subsequent vitamin D deficiency 13,14 , reduced physical activity and/or exercise 15,16,17 , reduced contact with parks and other green space 18,19,20 , and social isolation 21,22,23 .…”

Creating a Regional Nature Park: A Case Study on Community Engagement in Developing the Mill Creek Nature Park in the Town of Riverview, New Brunswick

“…Park space is a crucial thread in the fabric of a community, providing benefits to health through mental rejuvenation (Salmond et al, 2016;Cohen-Cline, Turkheimer, & Duncan, 2015) and opportunities for active recreation (Niemela, 1999); a place for wildlife and vegetation to flourish (Toni & Duinker, 2015); a space that can absorb air pollution (Chang & Li, 2014); a booster of land value (Brambilla & Ronchi, 2016); and a wellspring of economic opportunity (Sander, 2016). Subsequently, allocating resources for the establishment of these spaces should be the priority of all municipalities; however, creating an effective park requires more than just spare land and political will.…”