Summary: Living near areas with a higher tree canopy is linked to lower psychological distress and better self-rated general health.
Source: JAMA
Overview: An observational cohort study examined associations between urban green space and mental and general health. Prior research has suggested that nearby green space can offer health benefits; this study explored whether different types of vegetation—tree canopy, grass, and low-lying plants—differently relate to mental well-being and overall health.
The analysis included 46,786 city-dwelling adults in Australia, drawn from the Sax Institute’s 45 and Up Study. Researchers measured the percentage of total green space, tree canopy, grass, and other low-lying vegetation within a 1.6-km (1-mile) road-network buffer around each participant’s residential address at baseline, and assessed health outcomes at baseline and again about six years later.
Three health outcomes were evaluated: (1) risk of psychological distress using the 10-item Kessler Psychological Distress Scale, (2) self-reported physician-diagnosed depression or anxiety, and (3) fair to poor self-rated general health. The study considered both prevalence at baseline and incidence at follow-up among participants without the condition at baseline.
The authors report that greater tree canopy was consistently associated with a reduced likelihood of psychological distress and with better self-rated general health. By contrast, no green-space measure showed a significant association with diagnosed depression or anxiety. Low-lying vegetation showed no consistent relationships with the outcomes. Surprisingly, higher proportions of grass within the buffer were associated with a greater likelihood of reporting fair to poor general health and with prevalent psychological distress in some comparisons.
Key limitations include reliance on self-reported health measures and potential changes in green-space availability over time that were not fully captured. These factors could bias results toward the null, possibly underestimating true associations.
Source:
JAMA
Media Contact:
Thomas Astell-Burt – JAMA
Image Source:
The image is in the public domain.
Original Research: Open access
“Association of Urban Green Space With Mental Health and General Health Among Adults in Australia,” by Thomas Astell-Burt, PhD, and Xiaoqi Feng, PhD. Published in JAMA Network Open. doi: 10.1001/jamanetworkopen.2019.8209
Abstract (Rewritten)
Importance
Emerging evidence suggests that living near green space can support mental and general health and might help prevent depression. However, most prior research is cross-sectional, and it is unclear whether specific types of green space (for example, tree canopy versus grass) matter more for health outcomes.
Objective
To determine whether total green space or particular types of urban vegetation are associated with better mental health and self-rated general health.
Design, Setting, and Participants
This cohort study analyzed a residentially stable, urban sample of 46,786 participants from Sydney, Wollongong, and Newcastle, Australia, enrolled in the Sax Institute’s 45 and Up Study. Baseline data were collected between January 1, 2006, and December 31, 2009, with follow-up from January 1, 2012, to December 31, 2015. Analyses were completed in January 2019.
Exposures
Researchers measured the percentage of total green space, tree canopy, grass, and other low-lying vegetation within a 1.6-km road-network buffer around residential addresses at baseline.
Main Outcomes and Measures
Outcomes included: (1) psychological distress risk (10-item Kessler Scale), (2) self-reported physician-diagnosed depression or anxiety, and (3) fair to poor self-rated general health. Each outcome was evaluated both for prevalence at baseline and for incidence at follow-up among those without the outcome at baseline.
Results
Participants had a mean age of 61.0 years (SD, 10.2), and 53.8% were female. At baseline, 5.1% of 37,775 participants reported high psychological distress, 16.0% of 46,786 reported diagnosed depression or anxiety, and 9.0% of 45,577 reported fair to poor health. Over a mean follow-up of 6.2 years, incidence rates included 3.3% for psychological distress (of 32,991), 7.5% for depression or anxiety (of 39,277), and 7.3% for fair to poor general health (of 40,741).
Adjusted analyses (controlling for age, sex, income, employment status, couple status, and education) indicated that living in areas with 30% or more total green space (OR, 0.46; 95% CI, 0.29–0.69) and higher tree canopy specifically (OR, 0.69; 95% CI, 0.54–0.88) were associated with lower incidence of psychological distress. Tree canopy of 30% or more versus 0%–9% was also associated with a lower incidence of fair to poor general health (OR, 0.67; 95% CI, 0.57–0.80). In contrast, areas with 30% or more grass (versus 0%–4%) were linked to higher odds of incident fair to poor general health (OR, 1.47; 95% CI, 1.12–1.91) and prevalent psychological distress (OR, 1.71; 95% CI, 1.25–2.28). Low-lying vegetation showed no consistent associations, and no green-space measure was associated with prevalent or incident diagnosed depression or anxiety.
Conclusions and Relevance
These findings suggest that protecting and restoring urban tree canopy—rather than generic greening—may be a promising strategy to promote community mental health and improve self-rated general health among urban residents.