London (CNN)City children who have daily exposure to woodland have better cognitive development and a lower risk of emotional and behavioral problems, according to a new study published in Nature Sustainability.
City children have better mental health and cognition if they live near woodlands
Researchers studied 3,568 adolescents aged 9 to 15 at 31 schools across London over four years to examine the associations between natural environments and cognitive development, mental health and overall well-being.
Using vegetation satellite data, researchers calculated adolescents' daily exposure to "green space," like woods, meadows and parks, and "blue space," including rivers, lakes and the sea, within 50 meters (164 feet), 100 meters (328 feet), 250 meters (820 feet) and 500 meters (1,640 feet) of their home and school.
A higher daily exposure to woodland was associated with higher scores for cognitive development -- measured through a series of memory-based tasks -- and a 17% lower risk of emotional and behavioral problems two years later, researchers said, adding that they adjusted for other variables, such as age, ethnic background, gender, parental occupation, type of school and air pollution.
Exposure to green space was associated with a beneficial contribution to young people's cognitive development, researchers explained. The same associations were not seen with exposure to blue space -- though the sample of children studied generally had low access to it, researchers noted in the study published Monday.
Lead author Mikaël Maes said that, while the team had established an association between woodlands and better cognitive development and mental health, there is no causal link between the two -- something that could be studied in the future.
"Currently, the mechanisms why humans receive mental health or cognition benefits from nature exposure is unknown. Scientific research on the role of the human senses is key to establish a causal link," Maes, a PhD researcher at University College London's school of Geography, Biosciences and Imperial College London School of Public Health, told CNN.
Maes said in an email that one possible explanation for the link between woodland, cognition and mental health could be that audio-visual exposure through vegetation and animal abundance -- which are more common in woodland -- provides psychological benefits.
However, there were limitations to the study. The team said the research assumed that living or going to school near natural environments meant more exposure to them, which may not always be the case. Area crime rates were also not taken into account.
Researchers also noted that more than half of participants had parents who had a managerial or professional occupation, meaning that adolescents in other socio-economic groups could be underrepresented in the study. Pupils with special educational needs could also react differently than peers represented in the research.
"The findings are impressive and do highlight the importance of time outside on such a scale," Carol Fuller, head of the Institute of Education at the University of Reading, told CNN via email.
"That said, while the findings are encouraging, what we don't get from the study is a sense of why we see the results that we do? While the authors speculate as to the reasons, there is a crucial need to engage directly with young people to understand the results from the perspective of those who were taking part," Fuller, who was not associated with the research, said.
"The research adds to a growing body of work about the importance of being outside on things like confidence, resilience, and self-efficacy," she said.
"It makes sense that if you can develop these skills, things like cognition and learning outcomes will then improve. Being outside allows young people to learn a range of different skills and engage in diverse experiences, important for developing these underlying traits," she added.
Stella Chan, professor of Evidence-based Psychological Treatment at the University of Reading, said in an email to CNN that the research offered "novel insights" with "potential to inform how we may better support young people's intellectual development, health, and wellbeing."
"As the authors note, just because someone lives close to natural environments does not mean that they could or would access this space, and of course how people use the space is another big question to ask," Chan, who was not involved in the study, said.
"Building on these findings, it would be important to investigate how factors that are associated with exposure to natural environments, such as physical activity and hanging out with friends, may help enhance teenagers' resilience, health, and wellbeing," Chan said.
The great outdoors has long been linked to good physical and mental health -- a 2015 study showed that people who take walks in nature report fewer repetitive negative thoughts.
And a 2019 study found that spending two hours a week soaking up nature -- be it woodland, park or beach -- gives a positive boost to health and well-being, both mentally and physically.