Protection and restoration of tree canopy in urban green spaces appeared to promote community mental health, according to a longitudinal cohort study in Australia.
“Simply being in, nearby, or with a view of green space may help to build capacities for better mental health, contribute to restoration of depleted cognitive capacities, enhance recovery from periods of psychosocial stress, and even increase optimism,” Thomas Astell-Burt, PhD, and Xiaoqi Feng, PhD, of the University of Wollongong School of Health and Society, Australia, wrote in JAMA Network Open. “The presence of a particular type of green space may be an important condition for supporting several of these domain pathways.”
Researchers examined whether total green space or specific types of green space were linked to better mental health in a sample of 46,786 city-dwelling participants aged 45 years and older from Sydney, Wollongong, and Newcastle, Australia. Data were collected from 2006 through 2009 and follow-up was conducted from 2012 through 2015.
Astell-Burt and Feng calculated the percentage of total green space, tree canopy, grass and other low-lying vegetation near residential addresses at baseline. They examined the risk for psychological distress (via the Kessler Psychological Distress Scale), diagnosed depression or anxiety and self-rated general health at baseline and follow-up.
Overall, 9,822 participants had 30% or more total green land cover within 1 mile of home; 11,957 had 30% or more tree canopy; and 2,038 had 30% or more grass within the same distance from home.
After adjusting for confounders, the researchers found that exposure to 30% or more of tree canopy compared with 0% to 9% was linked to a 31% lower risk for incident psychological distress (OR = 0.69; 95% CI, 0.54-0.88) and exposure to 30% or more grass was linked to a 71% higher risk for prevalent psychological distress (OR = 1.71; 95% CI, 1.25-2.28). Similarly, compared with participants exposed to 0% to 9% of tree canopy, those exposed to 30% or more were also less likely to have worse general health (OR = 0.67; 95% CI, 0.57-0.8). However, no green space indicator was linked to diagnosed depression or anxiety, according to the study.
“Our findings suggest that urban greening strategies with a remit for supporting community mental health should prioritize the protection and restoration of urban tree canopy,” Astell-Burt and Feng wrote. “In addition, the promotion of equal access to tree canopy may provide greater equity in mental health.”
The increasing density of people living in urban areas may result in less nearby green space and thus hinder with the health benefits provided, Sjerp de Vries, PhD, of Wageningen University & Research in the Netherlands, explained in an invited commentary.
“If so, an adequate provision of green space is perhaps better defined in terms of amounts per capita rather than in terms of amounts as such,” de Vries wrote. “Given this potential consequence, the relevance of green space offering peace and quiet for its mental health benefits seems an important topic for further investigation.” – by Savannah Demko
Disclosures: Astell-Burt and Feng report grants from Hort Innovation Ltd. and National Health and Medical Research Council. de Vries reports no relevant financial disclosures.