Getting out in green spaces is REALLY good for our mental and physical health
Greeting family, I hope this message finds you well. On the subject of wellness, my most recent video focuses on the demonstratable health benefits of going out into green spaces.
In the first part of the video, I discuss study which showed that the amount of greenery in a neighbourhood is negatively correlated with the number of fatal police shootings. In other words the more greenery, the less police shootings. This might seem like an obvious point. After all, more socially-deprived areas tend to also be less leafy. However, this study uses regression analysis to compare neighbourhoods with the same socioeconomic profile, the same racial demographics, the same crime rates, the same population density, the same levels of firearm ownership, and several other variables. When all of these are controlled, the areas with more greenery had less fatal police shootings. And the link was strongest when comparing the most deprived areas only.
This is a nuanced point but it’s important to grasp - the correlation has nothing to do with other socioeconomic factors. Let’s read from the report:
“The authors offered several explanations for these findings. One possibility is that green spaces reduce stress, anxiety, and mental fatigue—both for residents and potentially for police officers—making aggressive interactions less likely. Green surroundings may also give the impression that a neighborhood is more cared for and less dangerous, which could influence how officers perceive risk during encounters. Additionally, green spaces often encourage social interaction and community cohesion, which may enhance informal social control and reduce tensions that lead to police involvement.
“It may be surprising for many people to see our findings,” Jiang said. “However, many previous studies in the fields of environmental psychology and environmental behavior suggest that greener neighborhoods and cities can facilitate positive emotions, mental relaxation, social trust, social support, and natural surveillance among residents.”
“In contrast, barren neighborhoods and cities can stimulate suspicion, anger, frustration, a sense of unsafety, violent behaviors, deviant behaviors, and many other negative mental states and actions. Our findings are strong and reasonable. However, this is a fresh message for society because the impacts of green landscapes on fatal police shootings have not been well investigated before.” https://www.psypost.org/surprisingly-strong-link-found-between-neighborhood-greenness-and-police-shootings/
So let’s dig into the scientific evidence on the link between greener spaces and mental and physical heath.
Correlations between neighbourhood Green Spaces and Better Health
It’s been widely observed that the amount of nature in residential areas is correlated with positive mental and physical health:
“A growing body of epidemiological evidence indicates that greater exposure to, or ‘contact with’, natural environments (such as parks, woodlands and beaches) is associated with better health and well-being, at least among populations in high income, largely urbanised, societies1. While the quantity and quality of evidence varies across outcomes, living in greener urban areas is associated with lower probabilities of cardiovascular disease2, obesity3, diabetes4, asthma hospitalisation5, mental distress6, and ultimately mortality7, among adults; and lower risks of obesity8 and myopia9 in children. Greater quantities of neighbourhood nature are also associated with better self-reported health10,11,12, and subjective well-being13 in adults, and improved birth outcomes14, and cognitive development15, in children.” https://doi.org/10.1038/s41598-019-44097-3
Correlations between time spent in Green Spaces and Health
Similarly, studies have shown that people who spend more time in nature tend to have better health outcomes. One study from 2019 found that regardless of how much greenery was in the areas people lived in, those who spend 120 minutes a week in nature were 60% more likely to report positive health, and 23% more likely to report positive wellbeing. https://doi.org/10.1038/s41598-019-44097-3
Evidence for a causal connection between time in nature and health
But as the saying goes (please memorise this) “correlation doesn’t necessarily prove causation.” Just because two things are correlated doesn’t mean that one definitely causes the other. It could be that people who are already more healthy tend to live in areas with more greenery, and tend to spend more time in nature. So let’s look at some research that has indeed demonstrated causal links between time spent in green spaces, and positive health outcomes.
A 2009 study by researchers in Japan demonstrated that walking or viewing forest areas led to numerous improvements in the functioning of the endocrine, nervous and cardiovascular systems, whereas walking or viewing urban areas did not.
“The term Shinrin-yoku was coined by the Japanese Ministry of Agriculture, Forestry, and Fisheries in 1982, and can be defined as making contact with and taking in the atmosphere of the forest. In order to clarify the physiological effects of Shinrin-yoku, we conducted field experiments in 24 forests across Japan. In each experiment, 12 subjects (280 total; ages 21.7 ± 1.5 year) walked in and viewed a forest or city area. On the first day, six subjects were sent to a forest area, and the others to a city area. On the second day, each group was sent to the other area as a cross-check. Salivary cortisol, blood pressure, pulse rate, and heart rate variability were used as indices. These indices were measured in the morning at the accommodation facility before breakfast and also both before and after the walking (for 16 ± 5 min) and viewing (for 14 ± 2 min)... The results show that forest environments promote lower concentrations of cortisol, lower pulse rate, lower blood pressure, greater parasympathetic nerve activity, and lower sympathetic nerve activity than do city environments” https://doi.org/10.1007/s12199-009-0086-9
And a 2015 study in the U.S. used self-reporting and neuroimaging to demonstrate that spending time in green spaces led to reductions in rumination. Rumination is an excessive focus on the causes and consequences of ones emotions—most often, negative, self-relational emotions. Rumination is associated with activity in a part of the brain called the subgenual prefrontal cortex or sgPFC. The results showed:
Participants who went on a 90-min nature walk showed reductions in self-reported rumination and decreases in sgPFC activity, whereas those who went on an urban walk did not show these effects. Given the documented link between rumination and risk for depression and other psychological illnesses, the reduction in rumination among those with the nature experience suggests one possible mechanism by which urbanization—which reduces opportunities for nature experience—may be linked to mental illness. This suggestion draws support from our finding that at a neurobiological level, nature experience led to decreases in sgPFC activity, a brain region that previously has been shown to be associated with a self-focused behavioral withdrawal linked to rumination in both depressed and healthy individuals.” https://doi.org/10.1073/pnas.1510459112
What exactly happens in our bodies when we go out in nature?
In the rest of my video, I suggested that the reason spending time in green spaces boosts our health, is to do with light. I propose that when in green areas, we are bathed not only in sunlight coming directly down onto us from above, but also the sunlight that trees and green plants reflect onto us. I showed that green plants reflect most of the longer wave sunlight which we call near infrared and which is invisible to humans. I’ve previously looked at the link between mitochondria, melatonin and near infrared light in this video:
Finally, emerging clinical evidence is building our understanding of the ability of red light and especially near infrared light to positively impact human health due to it’s ability to penetrate deeply into our bodies. One area is Dementia, and here’s a good lecture on some of this work:
I appreciate your time and I hope I’ve stimulated lots of thought!
Peace
Ely