Imagine a drug that could substantially reduce hospital admissions for mental health disorders like psychosis, dementia and substance use-associated disorders.
We would be falling over ourselves to prescribe and recommend it as the benefits of reduced hospital admissions would cascade from individuals to families to society and the economy.
Now imagine that this reduction in hospital admissions could be achieved by just making some green space accessible to people in an urban area. A 10 per cent increase in local “greenness” was recently shown to be associated with a 7 per cent reduction in hospital admissions for all-cause mental disorders.
Recent research published in the British Medical Journal demonstrates the substantial and widespread benefits to people’s health from local nature. While there has been previous research showing the benefits of spending time in nature for individuals, this study is one of the most comprehensive and widespread demonstrations of the direct medical benefits.
RM Block
The authors used data on more than 11 million hospital admissions for mental disorders from over 6,800 locations in seven countries in the northern and southern hemispheres, together with satellite data on the abundance of vegetation in the same locations.
With more than half of humans living in cities, it was particularly interesting to see that the protective benefits of living in areas with more vegetation were more consistent in urban areas. This may be because green spaces in cities are usually more structured and accessible.
How we interact with green spaces varies with the climate, season and weather. In tropical and temperate regions where temperatures are relatively stable throughout the year, there was a stronger association between mental health and greenness during the colder season.
Outdoor activities in parks, woods, natural and semi-natural areas in cities in winter could therefore be particularly beneficial. Even having and interacting with houseplants in the cooler season could be helpful.
The broader benefits of interacting with plants through all our senses, including sight, touch and smell, are explored by Prof Kathy Willis in the book Good Nature. She outlines the mechanisms through which our sensory experiences of plants lead to improvements in our mental and physical health.
Plants can modify our microbiomes, those communities of bacteria and fungi in our guts and on our skin that work together with our bodies to keep us healthy. Our microbiomes are assembled mainly from our environment and can be modified by genetics and diet.
The plants, animals and soil that we encounter change the microbial communities on our skin and can also be breathed in or ingested with food. Several years of research have shown that a diverse microbiome, which can be assembled from interactions with natural areas, plants and soils, is associated with better functioning immune systems.
The benefits of having nature in our lives could even extend to the construction of our houses. Plants release chemical compounds into the air, and we detect some of these as the scents of flowers or the distinctive smell of a Christmas tree. Other plant chemicals do not have an immediate “smell” but nevertheless can have mental and physical effects on us.
Research on breathing in the smell of conifers in particular shows that this has a relaxing effect. The scent of cypress trees has also been shown to increase the number of “natural killer” immune cells in our blood. It is entirely possible that a move to more wooden houses and furniture will have important co-benefits for our health.
We can harness this power of nature for health through the conservation of natural areas, restoration of nature and by designing our cities, gardens and houses to incorporate the benefits of plants. As we take climate action to protect the carbon stored in forests, we can also gain very substantial public health benefits. Reducing deforestation in Brazil was shown to significantly reduce malaria incidence and restoration and conservation could decrease malaria cases by up to 50 per cent.
Stack the benefits of a walk this winter, get out with family or friends, inhale the scents of nature, listen to the birds, hug a tree and connect with the Earth. This prescription is not just wellness woo; there is scientific support for a closer sensory relationship with plants.
- Yvonne Buckley is co-director of the Co-Centre for Climate + Biodiversity + Water and professor of zoology at Trinity College Dublin
