Nature provides both physical and psychological benefits. How does this healing through exposure to nature occur?
When the green woods laugh with the voice of joy,
And the dimpling stream runs laughing by;
When the air does laugh with our merry wit,
And the green hill laughs with the noise of it.
William Blake was onto something in his “Laughing Song” poem. We need green spaces. Not only are they pleasant to look at, but these spaces are also healing. Almost anyone who has spent substantial time in a forest, up a mountain, or along a river recognizes that this is healing.
Nature provides both physical and psychological benefits. Studies have shown improved healing in hospitals with green spaces outside windows rather than brick walls and decreased anxiety and increased workplace satisfaction in offices with plants and/or views of nature.1,2
How does this healing through exposure to nature occur? A variety of possible mechanisms have been proposed, from improved air quality to increased physical activity and enhanced social integration. Ming Kuo, PhD,3 has studied how green spaces affect humans and has postulated that there may be at least one common pathway toward wellness acting through the immune system.
The immune system has been implicated in depressive and anxiety disorders, as well as other mental and physical health problems. Certainly, reduced air pollution, increased physical activity, and improved social ties may all occur with an increase in green spaces and are associated with improved functioning of the immune system. In addition, plants produce antimicrobial organic compounds called phytoncides that change autonomic function and increase immune functioning.4 Walks in the forest decrease inflammatory cytokine levels.5 Images of nature have been shown to increase parasympathetic activity and to reduce sympathetic activity.6 These changes in nervous system activity improve both sleep and immune function.
Ruminative processes and the subgenual prefrontal cortex may also be involved. In persons who are predisposed to depression, the mind frequently wanders into a ruminative pattern of negative, self-referential thoughts and emotions. The subgenual prefrontal cortex has demonstrated increased activity during rumination (in healthy and depressed individuals) and has been found to have increased connectivity to the default mode network in those with depression. In a study by Bratman and colleagues,7 walking in green spaces as compared with walking in urban spaces was associated with reduced activity in the subgenual prefrontal cortex, accompanied by a decrease in rumination.
As of 2017, approximately 82% of the US population lives in urban areas.8 Increased urbanization has been associated with a rise in a variety of mental illnesses, although the etiology is not fully understood and the mechanisms are likely diverse.
Greater exposure to green spaces may help improve mental and physical well-being. Physicians have begun to prescribe time in nature to their patients-I encourage my patients to get outside daily and into nature. Some of the innovative programs that exist to “prescribe” green spaces are available at: https://prescriptiontrails.org/ and http://www.gwaparkrx.com/.
Urban green spaces can help mitigate the effects of climate change. Cities account for much of the carbon dioxide emissions on our planet. Green spaces sequester carbon in plants, soil, and water. They also mitigate the effects of urban heat islands, which develop where buildings, parking lots, roads, and other infrastructure have created impermeable and dry areas where vegetation once grew. These areas are hotter than rural areas nearby. Urban heat islands pose a risk to human health because of higher temperatures and are associated with an increase in energy used to cool spaces. Trees and other vegetation lower the risks and costs of urban heat islands by reducing temperatures.
Despite the importance of green spaces, they are rapidly being eliminated. Cities are expanding, and green spaces are being chopped down and paved over.
For the health of our patients and our planet, we need to expand our green spaces, not keep paving them over. As psychiatrists, we can advocate for the creation, expansion, and protection of green spaces. Using our voices as patient and public health advocates is an extremely important tool. Reach out to city councils, local representatives, and groups advocating for green spaces, and let them know your concerns. Educate others in your work setting about the importance of green spaces and, if you don’t have a green space, develop a team to work on creating one. Your patients, your community, your planet, and your body will all thank you.
Dr Young is Associate Professor at the Northern Ontario School of Medicine in Canada. She is a member of the Climate Psychiatry Alliance and the Canadian Climate Psychiatry Alliance. Dr Young reports no conflicts of interest concerning the subject matter of this article.
1. Ulrich R. View through a window may influence recovery from surgery. Science. 1984;224:420-421.
2. Nieuwenhuis M, Knight C, Postmes T, SA Haslam. The relative benefits of green versus lean office space: three field experiments. J Exp Psychol Appl. 2014;20:199-214.
3. Kuo M. How might contact with nature promote human health? Promising mechanisms and a possible central pathway. Front Psychol. 2015;6:1093-1098.
4. Li Q. Effect of forest bathing trips on human immune function. Environ Health Prev Med. 2010;15:9-17.
5. Im SG, Choi H, Jeon YH, et al. Comparison of effect of two-hour exposure to forest and urban environments on cytokine, anti-oxidant, and stress levels in young adults. Int J Environ Res Public Health. 2016;13:1-11.
6. Brown DK, Barton JL, Gladwell VF. Viewing nature scenes positively affects recovery of autonomic function following acute-mental stress. Environ Sci Technol. 2013;47:5562-5569.
7. Bratman GN, Hamilton JP, Hahn KS, et al. Nature experience reduces rumination and subgenual prefrontal cortex activation. Proc Natl Acad Sci U S A. 2015;112:8567-8572.
8. World Bank Group. Urban population (% of total). United Nations Population Division. World Urbanization Prospects: 2018 Revision. https://data.worldbank.org/indicator/SP.URB.TOTL.IN.ZS?end=2017&start=2009. 2018. Accessed July 10, 2019.