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Author: Jeremy A Lewis (BA psychology, MPH epidemiology, MLA student class of 2027)

A fascinating paradigm in healthcare and social services called social prescribing views time in nature among other social or recreational activities as a complement to modern medicine (1). As a response to the social or behavioural factors that powerfully influence many medical conditions (2), this movement involves doctors or other health professionals writing prescriptions for activities including time spent in green space or natural areas (1). Growing (but not yet definitive) evidence shows benefits of nature exposure for cognitive functioning and mental health (3), making activities like walking groups, community gardening, or time spent in parks sensible options for social prescribing (1).

For me, the term “social prescribing” evokes a metaphor. It brings to mind a doctor writing a prescription for pills – I pick the pills up at the pharmacy and in short order they make me feel better. Is this a good metaphor for the health benefits of time spent in nature? While powerful, that analogy paints the wrong picture of how exposure to nature really affects people. That’s because the effect of nature on health, even more so than medical drugs (think of the well-understood placebo effect), depends on the meaning derived from the experience. A more useful metaphor for nature in connection with human health is to consider nature as a friendship. That might sound grammatically awkward, but that’s the point – we tend to think of nature as a thing, but to unpack it’s relevance to health we need to understand it as a relationship.

To be fair, some social prescribing scholarship (e.g., source 1) offer a nuanced accounts of how outdoor activities affect health, considering social, psychological and societal mechanisms in conjunction with biology. However, on other occasions that nuance is lost, with scholars opting for a simple exposure-response model, more like what we expect from a medical pill.

That simplistic metaphor – nature as a pharmaceutical drug – prompts research that cannot fully describe the way that nature benefits human health. A rigorous literature review on the effect of nature exposure on human health (3), called for more standardized measures of nature exposure, even as some of the most scientifically careful studies on the topic have already taken pains to standardize their environmental interventions. For example, a study of vacant lot greening in Philadelphia USA (4) standardize their landscape intervention for vacant sites to include trash clean up, site grading, turf grass and caliper-sized tree installation, and the installation of a wooden perimeter-fence. If nature exposure were like a medical drug, then standardizing it’s delivery would make perfect sense — we could treat our issues with the right dose from a standard recipe of outdoor recreation and measure its effect in a scientifically elegant way. But because the effect of nature depends on our relationship to it, standardization could miss the point entirely.

The standardized landscape intervention in the Philadelphia vacant lot study (4) could be viewed as a methodological strength, allowing the scientists to measure the effect of a well-understood intervention. However, widening our view to consider future studies, surely we need to understand the effect of may other types of landscape interventions and not simply reproduce this greening effort for new populations? Nature or green space is like a friendship, and turf grass and caliper trees are not the only type of friend that we need to get acquainted with. Some people may prefer other, wilder, personalities even as others may prefer these tidier spaces.

If nature is like a friendship and not a pill, we should understand and study it as such. Rather than trying to understand the effect of nature exposure, holding steady what we do in nature and the relationship we have with it, we should instead examine the joint effect of being in relationship with nature. For example, a survey based study in the UK found evidence that psychological connectedness with nature and the tendency to do simple nature-appreciation activities such as stopping to smell the flowers was more strongly associated with wellbeing and mental health than mere time reported in nature, while time in nature remained linked to self-reported physical health (5).  

It strikes me that vastly different study designs are needed to understand the effect of our relationship with nature, as opposed to mere “exposure” to nature. In particular, because relationships are built over the life course, long-term studies would be needed to understand how our relationship with nature is developed over time, and once that relationship has established, how it might moderate the health benefits that nature provides. Although I did not find examples of studies like this when researching this article, here are some ideas for how this could be studied. We might find people with specific relationships with nature (outdoor adventure athletes, people who grew up camping, people who have worked outside, or people from varied cultural or geographic backgrounds) and compare their benefits from nature versus other peoples’. Alternatively, we could compare the health or wellness consequences of temporarily restricting time spent outdoors between people with different life-experiences with nature (such as among outdoor adventure athletes versus other athletes, for example). Better yet, we could evaluate interventions that help people build certain beneficial relationships with nature, whether explicitly therapeutic, recreational, food based, environmental science based, or outdoor adventure based and measure the long term effects on health and wellness of those relationships. While long term intervention studies can be unattractive to scientists due to their expense and methodological complexity, they would likely be the most rigorous way to understand the effect of nature-relationships on health and wellness.

A paper describing two pilot studies of European outdoor adventure programs for youth and young adults did an excellent job of describing  the nuanced pathways that can lead nature-based experiences to benefit participants (6). Far from assuming that mere exposure to the outdoors will lead to meaningful benefits, outdoor education scholars generally understand that the meaning of these experiences is critical for achieving desirable outcomes. In particular, participants on outdoor adventure trips are guided to face challenges that they self-selected, and that while uncomfortable can ultimately be overcome (think how different this is from many everyday challenges). Working through these types of challenges is theorized to enhance mental health and resilience as it builds a sense of self-efficacy. Indeed, although methodologically limited by only short-term follow-ups and small samples, the two European outdoor adventure pilot studies mentioned earlier that focused on hiking and outdoor survival skills resulted in increased mindfulness, reduced stress, increased self-efficacy, increased happiness and increased life satisfaction among the youth and young adult participants (6). 

In arguing that people differ in their preferences for outdoor places and relationship with nature, I am not suggesting that all types of places are equally hospitable. There are qualities of places that we can all recognize as inviting or off-putting. Some places are downright inhospitable, without protection from wind, sun, or rain, or in contrast lacking natural light entirely. Some places are teaming with biodiversity and interest, while others are riddled with cracked, hot concrete. One useful type of study compares the effect various outdoor environments on health or wellness – for example a fascinating study based out of Aukland New Zealand looked at the effect of time spent in a relatively biodiverse sensory garden with an enriching design, compared to a paved plaza for stress, wellbeing and productivity (7).  Although I don’t report the findings of the sensory garden study (7) here due to methodological limitations, the question it asks is a useful one – not simply “what is the effect of time outdoors on health and wellbeing?”, but, “what is the differential effect of various outdoor environments on health and wellbeing?”. Another study found that urban bird diversity, an indicator of vegetative complexity and ecological complexity more broadly, was associated with higher housing prices (8). This study shows the connection between biodiversity and human habitation preferences, although for methodological reasons it does not clarify the exact causal relationship between the two. More research is needed, but it’s safe to say that while people differ in what they’re looking for in outdoor places, there are some qualities that most of us tend to prefer. 

Like a friendship, our relationship with nature is situated in both our individual and cultural histories, a point vividly illustrated by many Indigenous accounts of nature. Rather than a resource to consume exclusively for our own benefit, Robin Wall Kimmerer in “Braiding Sweetgrass” discusses the deep relationship that herself and her People, The Potawatomi, have with the land (9). These relationships encompass the full connection between nature and health — nature is not just a place for outdoor recreation, but the source of food, building material, Indigenous language and stories, cultural memories and life experience. In Kimmerer’s account, friendship is not an analogy for the relationship to nature, but rather many Indigenous people view themselves as truly “in relationship with the land”. Kimmerer’s description of collecting strawberries in a field near her home as a child, canoe camping with her family, or teaching her university students about companion planting with the three sisters (corn, squash and climbing beans), vividly ties her experience of nature to both her own life experience and to cultural memories that have been transmitted between generations of Indigenous people through language and stories. In this account, nature is medicinal not like a pharmaceutical pill, but instead like a relationship that is steeped in cultural and personal history.

Acknowledging the contingency of humanity’s survival upon our relationship with nature, we might wonder if the importance of nature exposure for health is too obvious to bother studying? However, in the reality that many of us live in the modern world, where we insulate ourselves in sanitized and climate-controlled houses, surrounded by manicured lawns, a short drive from shelves lined with plastic wrapped food, it is worth asking what the mental and physical health effects of time in nature may be. To meaningfully address these important questions, consumers and producers of research should think of nature like a friendship that we navigate throughout life – one situated in a cultural, socioeconomic and individual context – not like a pharmaceutical drug that we react to based on dose alone.  

References

1.           Leavell, M. et al. Nature-based social prescribing in urban settings to improve social connectedness and mental well-being: a review. Curr. Environ. Health Rep. 6, 297–308 (2019).

2.           Social determinants of health. World Health Organization https://www.who.int/health-topics/social-determinants-of-health.

3.           Jimenez, M. P. et al. Associations between nature exposure and health: a review of the evidence. Int. J. Environ. Res. Public. Health 18, 4790 (2021).

4.           South, E. C., Hohl, B. C., Kondo, M. C., MacDonald, J. M. & Branas, C. C. Effect of Greening Vacant Land on Mental Health of Community-Dwelling Adults: A Cluster Randomized Trial. JAMA Netw. Open 1, e180298–e180298 (2018).

5.           Richardson, M., Passmore, H.-A., Lumber, R., Thomas, R. & Hunt, A. Moments, not minutes: The nature-wellbeing relationship. Int. J. Wellbeing 11, (2021).

6.           Mutz, M. & Müller, J. Mental health benefits of outdoor adventures: Results from two pilot studies. J. Adolesc. 49, 105–114 (2016).

7.           Souter-Brown, G., Hinckson, E. & Duncan, S. Effects of a sensory garden on workplace wellbeing: A randomised control trial. Landsc. Urban Plan. 207, 103997 (2021).

8.           Farmer, M. C., Wallace, M. C. & Shiroya, M. Bird diversity indicates ecological value in urban home prices. Urban Ecosyst. 16, 131–144 (2013).

9.           Kimmerer, R. W. Braiding Sweetgrass: Indigenous Wisdom, Scientific Knowledge and the Teachings of Plants. (Milkweed editions, 2013).