Tree-covered neighborhoods linked to lower ADHD risk in children

A new study published in the Journal of Environmental Psychology has found that exposure to greenspace may be indirectly associated with a lower likelihood of being diagnosed with attention deficit hyperactivity disorder (ADHD). The research offers new insights into the potential benefits of natural environments on children’s neurodevelopment and suggests that promoting greenspace in urban settings could help support mental health in children.

ADHD is a common neurodevelopmental disorder, affecting 5–7% of children worldwide. The condition is characterized by symptoms of inattention, hyperactivity, and impulsivity. Children diagnosed with ADHD often face additional challenges, such as difficulty in social, educational, and occupational settings, as well as an increased risk of developing other psychiatric disorders.

Given the variety of genetic and environmental factors that contribute to ADHD, researchers have explored protective influences, such as exposure to natural environments and physical activity. Previous studies have shown that greenspace can benefit mental health by reducing stress and enhancing cognitive functioning.

However, the exact mechanisms by which exposure to greenspace might influence ADHD diagnosis have remained unclear. The researchers aimed to explore these mechanisms, particularly focusing on how greenspace might lead to increased physical activity and social cohesion, which are known to support healthy neurodevelopment.

The study was part of a broader project called NeuroSmog, which aimed to assess the effects of environmental factors like air pollution on the neurodevelopment of children. The data were collected between October 2020 and September 2022 from 689 children aged 10–13 years living in southern Poland. These children were divided into two groups: those diagnosed with ADHD and those without the condition. The ADHD group consisted of children referred by psychologists, doctors, or parents, while the control group was randomly selected from local schools.

All children underwent a thorough psychological assessment, administered by experienced clinical psychologists, to diagnose or rule out ADHD based on the latest international guidelines. The assessment included various cognitive and behavioral measures, such as tests of memory, attention, and executive functioning. Parents were also asked to complete surveys about their children’s behavior, neighborhood environment, and levels of physical activity.

The researchers used land cover data from 2018 to measure the greenspace around the children’s homes, specifically focusing on tree cover and grass or shrub cover within 500 meters of their residences. They also collected information about whether the children had a garden at home. To understand how greenspace might impact ADHD, they analyzed several factors, including perceived greenspace, neighborhood safety, social cohesion, and physical activity.

The researchers did not find a direct link between the amount of greenspace and ADHD diagnosis. However, they identified an indirect pathway in which tree cover was associated with higher levels of physical activity, and this physical activity was linked to a lower likelihood of ADHD diagnosis. This suggests that tree-covered areas might encourage children to be more physically active, which in turn could have positive effects on their neurodevelopment.

In addition to tree cover, the presence of a garden at home was associated with a higher perception of greenspace, which contributed to stronger feelings of neighborhood social cohesion. Social cohesion refers to a sense of trust, support, and connectedness within a community, and previous research suggests it plays a role in promoting mental health. However, the study did not find a significant link between perceived social cohesion and ADHD diagnosis, meaning that while social cohesion might be an important factor for general well-being, it may not directly influence ADHD outcomes.

Interestingly, the study found that grass cover, unlike tree cover, did not show any significant association with physical activity or ADHD diagnosis. This aligns with earlier research suggesting that different types of greenspace might have varying effects on health. Tree cover, with its added features like shade and biodiversity, might offer more stimulating and attractive environments for children to play and engage in physical activities compared to grassy areas.

While the study presents important insights, it also has several limitations that should be considered when interpreting the findings. First, the study relied on parental reports for certain measures, such as physical activity and perceptions of greenspace, which may introduce some bias.

The researchers also pointed out that the types of greenspace matter. For instance, the study focused on natural tree cover and gardens but did not account for structured greenspaces like parks or playgrounds, which might offer different benefits for children’s mental health. In future research, it would be valuable to explore how various types of greenspaces, including urban parks, forests, or other recreational areas, contribute to ADHD outcomes.

Another key direction for future research involves understanding the long-term effects of greenspace exposure on neurodevelopment. The current study was cross-sectional, meaning it captured a snapshot of children’s lives at one point in time. To establish a clearer link between greenspace and ADHD, longitudinal studies are needed to follow children over time and observe how changes in their environment might impact their cognitive and behavioral development.

Nevertheless, the study adds to a growing body of evidence suggesting that exposure to greenspace, particularly tree-covered areas, can play a role in promoting physical activity and supporting neurodevelopment in children.

“Our findings suggest an association between exposure to greenspace, specifically, tree cover, and ADHD diagnosis, which is mediated by [physical activity],” the researchers wrote. “These findings suggest that access to natural environments enabling [physical activity] should be protected and promoted as it may support normal neurodevelopment… City planners should therefore prioritize access to greenspace in urban architecture to decrease mental health burden in urban child population.”

The study, “Lifelong greenspace exposure and ADHD in Polish children: Role of physical activity and perceived neighbourhood characteristics,” was authored by Dorota Buczyłowska, Nitika Singh, Clemens Baumbach, Jakub Bratkowski, Yarema Mysak, Maja Wierzba-Łukaszyk, Katarzyna Sitnik-Warchulska, Krzysztof Skotak, Małgorzata Lipowska, Bernadetta Izydorczyk, Marcin Szwed, Iana Markevych, and Angel M. Dzhambov.