There is no single solution to the world-wide epidemic of poor mental health; addressing its root causes, like poverty-triggered stress and social isolation, and choosing effective treatment for sufferers remains paramount. One way to potentially partly buffer against the effects of poor mental health is through contact with nature, including the green spaces within metropolises.
This is an emerging area of research with plenty of unanswered questions attached, but there are a not-insignificant number of studies pointing to this being a measurable, important effect.
“Green space is an agent of public health, one that can build and sustain mental wellbeing,” Jenny Roe, an environmental psychologist at the University of Virginia, told Earther.
That’s why she’s part of a team that wants to not just quantify the effect that natural spaces have on mental health, but to also frame it in a way that forms part of designs for cities.
Neighbourhood architects, engineers, and policymakers look at all kinds of factors and needs when building a city, including transportation links, housing, aesthetics, amenities, and so forth. Natural spaces are also considered, for their aesthetic, recreational, and ecological benefits. A study published in July in Science Advances outlines a model that will let policymakers see nature’s impacts on psychological wellbeing in much the same way.
The relationship between nature, mental health, and general psychological wellbeing is still tenuous but a subject of much research, and for now, the framework designed to encapsulate these connections is merely a concept. But if the benefits of green spaces on mental health become clearer over time, then this framework certainly has potential.
Our relationship with nature is like those we have with our parents, siblings or co-workers, said Beth Collier, a nature-based psychotherapist and trustee of the National Park City Foundation. They have a huge impact on our psychological wellbeing, she said, whether we are explicitly aware of it or not.
According to the July study, “psychological wellbeing” factors in a range of components, including experiencing everyday pleasure and enjoyment, sentiments of optimism and accomplishment, a sense of purpose, meaning and fulfillment, a capacity to regulate emotions, and healthy relationships with others.
A range of studies on public cohorts of wildly varying sizes have suggested that experiences with nature can boost happiness and wellbeing. A study of 2,600 schoolchildren in Spain, for example, found that exposure to green spaces near a child’s home and school was associated with better working memory and attentiveness — one perhaps linked to a drop in air pollution exposure.
Another study of 2,500 Wisconsinites found green spaces correlate with fewer symptoms of anxiety and depression. A meta-analysis of 143 other studies looking at 100 different health outcomes found that green space exposure may correlate with lower cortisol levels. The paper didn’t look at mental health consequences, but prolonged high cortisol levels are linked to an increased risk of stress, anxiety, and depression.
Contact with nature is an anti-anxiety strategy, one that can have a positive effect on people with mental health problems, the Science Advances study co-author Howie Frumkin and head of the Our Planet, Our Health program at the Wellcome foundation told Earther. Green spaces can also help build social cohesion, he said, by bringing potentially lonely people together in a shared public space.
Frumkin noted that green spaces also indirectly promote more physical activity which itself is a defence against the effects of poor mental health. One study of 260,000 Australians found that physically active people in the greenest neighbourhoods were at lower risk of psychological distress, although it didn’t boost the psychological wellbeing of sedentary people.
That indirect effect is, however, emblematic of a key problem with this research: namely, it isn’t clear what aspects of green spaces can be definitively linked to these apparent boosts in psychological wellbeing. There are plenty of interlinked factors involved and each are troublesome to yank away and investigate in isolation from the complicated matrix of life.
Take this expansive study that assessed the wellbeing of nearly a million people in Denmark. It found that children who grew up in a green space-lacking neighbourhood had up to a 55 per cent greater risk of developing a range of mental disorders in adulthood. As the study’s authors themselves note, though, these risk estimates are fundamentally based on correlations. Correlation, as ever, isn’t causation; plenty of other factors, from access to basic resources and mental healthcare to family dynamics and socioeconomic backgrounds, affect mental health, too.
With this issue (among others) in mind, this 2018 review paper concluded that there isn’t much robust public health evidence that shows greening the urban environment improves mental health, quality of life or social isolation issues.
It is noteworthy, though, that the World Health Organisation’s official line is that green spaces are paramount to mental health, with access to them helpful in the treatment of psychological illness. If access to nature is a major determinant of psychological wellbeing, “then it is a necessity, not a luxury,” said Galt. “By logical extension, it is a human right.”
Scientific literature, says Frumkin, also suggests that the health benefits of contact with nature are larger for poor people than for the affluent. As it happens, said Galt, green space is distributed along lines of affluence. That means that this framework could address what is a pervasive issue of environmental justice. Racial and financial inequality can leave entire neighbourhoods and cities with poor quality of life.
Clearly, the impacts of the environment on mental health should be considered when building cities, Greg Bratman, an expert in psychology, public health, ecology, and recreation at the University of Washington and the July Science Advances study’s lead author told Earther. With this in mind, he and his colleagues conjured up a framework in which city planners can see how this can be achieved.
First, the team would set out what natural features are being considered. Say you’re dealing with trees—this step would outline their size, their type, how they will be arranged, how biodiverse they are, and so on. Then, the way in which people would be “exposed” to these trees would be described: will the density of trees be changed in a closed-off residential neighbourhood, or in a small city park open to all? How long will the contact with nature last?
Next, the framework will assess how the public will “experience” these trees. Will these trees be only be able to be seen, or walked around? This matters more than you may think; as the study points out, looking at water isn’t the same as swimming in water. This experience could also be seen in terms of having a “dose” of nature: how much of this available green space will be “absorbed” by individuals?
If this is all carefully quantified, then it could predict how a myriad of nature experiences would translate into specific mental health benefits. Officials, using pre-existing data, would be able to use this information to inform their city building.
Getting that vital data will require many different efforts at many different scales, said Bratman. Fortunately, various experiments in different countries are starting to come through.
Just take a recent randomised US trial in Philadelphia. There, some vacant city lots were turned into a green space, cleared of its trash, or left alone. Researchers found that the poor mental state of those near the greened urban spaces improved, something that could be quantified.
Frumkin gives another example: London has a census of urban trees and, thanks to the National Health Service, drug prescription data assigned to residential addresses. When compounding factors like socioeconomic status are taken into account, there appears to be a correlation between the density of the tree canopies and lower rates of antidepressant prescriptions, he claimed.
There are roadblocks to getting these sorts of rich datasets. The American healthcare industry is infamously chaotic, and this extends to its data. Frumkin said there is very little, if any, consistent, detailed, population-wide health data.
“That’s why so much of the really good research takes place in settings like the UK and Scandinavia, where there are rational healthcare systems,” he added.
Privacy is another issue. Data protection is obviously a good thing but Frumkin said that restrictive data access can make population health research harder. Over time, he suggested, we need to “balance our right to privacy as individuals with the fact that the data about us, when pooled, forms part of a common resource that’s good for us, collectively.”
In any case, much more research is needed before this framework can make significant strides in the real world. As the authors of the Science Advances study acknowledge, with the data currently available, the framework can only address average, population-level impacts. It’s yet not clear how various types of green spaces affect specific genders, age categories, and subpopulations who already have detrimental mental conditions.
Crucially, the framework cannot generalise, as no two cities or cultures are the same. Galt, who part of his career in parts of Africa, noted that some city dwellers see green spaces as hazardous, as they can be associated with dangerous animals or higher rates of crime. Not everyone will respond to natural spaces in cities open arms.
Even if they are viewed in an overwhelmingly positive light, green spaces still will always have to compete against other essentials . Space for housing is an example of something that is more urgent in the short-term than green space adaptations partly aiming to positively affect mental health. And even if green spaces win out, said Galt, they will need to be managed effectively, lest they inadvertently become waste dumps—a fate hardly conducive to good physiological or mental wellbeing.
There’s also no guarantee that cities will even be able to use this framework effectively. Often, the government department that budgets for green spaces is divorced from the department that commands the health budget. The connections between nature and mental health, said Frumkin, shows how siloed thinking needs to be replaced by more holistic governance.
Despite these obstacles, there is plenty of room for optimism. Policymaking is, unfortunately, largely driven by economic benefits. It’s worth remembering, then, that poor mental health impacts the economy, through treatment costs and lost productivity at work. If it’s recognised that green spaces could reduce this economic burden, perhaps officials will see the value in frameworks such as this.
At the same time, Galt argued that mental illnesses are being spoken about more openly than ever before, just as cities are recognising nature as essential infrastructure.
This recent sea change in perspective could be epitomised by the UK: This July, its capital was the first to sign up to a charter to make cities greener, wilder, and healthier.
“I don’t think conservationists ten, twenty years ago would have envisaged that the future mayor of London would have stood in City Hall in front of a packed audience and declared The Old Smoke a National Park City,” said Galt.
Addressing mental health will require far more than just greener cities. Social isolation and loneliness, reducing stress that comes from poverty and income equality, and improving how people are treated in workplace environments, among other things, also need tackling, said Frumkin. Nature, though, looks to have a key role to play.
“It’s only in the past 10,000 years—a blip in the evolutionary history of humans—that we have begun isolating ourselves from nature,” said Galt. “Physiologically and psychologically, we are still hardwired to the wilderness.”