Why Your Brain Needs a Walk in the Park: Residential Greenspaces as the Next Frontier in Brain Research and Treatment

Greenspaces—encompassing parks, gardens, and other green areas within residential neighbourhoods—might initially appear trivial within clinical and behavioural neuroscience research. Since the seminal study that started during the early twentieth century that first linked greenspaces to general health outcomes, ¹ this domain has experienced significant growth. By mid-2024, nearly a thousand studies had investigated the diverse connections between greenspaces and health, underscoring the relevance and expanding scope of this field.

Research has increasingly highlighted that proximity to greenspaces is positively associated with larger brain volumes, including total brain, grey matter, and white matter, across both adults ² and children. ³ For instance, children exposed to residential greenspaces demonstrate improvements in attention, including faster reaction times for both sustained and selective attention. Additionally, a broader radius of greenspace correlates with enhanced short-term memory and quicker visual processing. However, these positive associations can be moderated by long-term exposure, which diminishes some of the observed benefits. ⁴ In contrast, less neighbourhood greenspace has been associated with poorer spatial working memory in children, a trend consistent across both deprived and non-deprived areas. ⁵

The relationship between greenspaces and brain health in older adults reveals more nuanced findings. While increased greenspace in the years leading up to an MRI has been linked to a borderline reduction in ventricular enlargement, no significant effects were observed on other MRI measures or variations by APOE genotype or sex. ⁶ Nevertheless, increased greenspace has been associated with a reduced risk of Alzheimer’s disease and vascular dementia. The most pronounced reductions in risk are observed at higher levels of greenspace exposure, likely due to the associated lower levels of fine particulate matter. ⁷ Specific types of greenspaces also show promise: forest green space is linked to a reduced risk of mild cognitive impairment, while greater diversity in greenspaces correlates with a lower risk of developing dementia. ⁸ Increased residential greenspace has been associated with a 24% lower risk of dementia, though this effect diminishes after accounting for additional factors. Medium levels of greenspace also correlate with a 28% lower risk of dementia. ⁹

The benefits of greenspaces extend beyond cognitive health, impacting stroke risk as well. Greater residential greenspace is linked to a reduced risk of severe stroke. ¹⁰ A comprehensive study involving over 422,000 participants over 12.5 years found that increased residential greenspace was associated with lower risks of stroke, dementia, and comorbid conditions, with a particularly strong protective effect within the first year and persisting for several years post-onset. ¹¹ Additionally, a study of more than 61 million Medicare beneficiaries demonstrated that higher levels of vegetation, as measured by the Normalised Difference Vegetation Index (NDVI), were associated with a reduced risk of Alzheimer’s disease and related dementias (ADRD) hospitalisations. For Parkinson’s disease, increases in NDVI and park coverage were linked to lower hospitalisation rates, although effects varied based on demographic factors. ¹²

Socio-economic factors also intersect with greenspace and brain health. Neighbourhoods with lower greenspace and income levels tend to experience more pronounced reductions in white matter grade as compared to those with higher levels of both greenspace and income. ¹³

Despite notable advancements, several limitations in greenspace research require attention. Variability in how greenspaces are defined and measured across studies complicates comparisons and generalisations. Many studies rely on indirect metrics, such as satellite imagery or self-reported exposure, which may not fully capture the quality or usability of greenspaces. Although numerous studies have made strides in controlling for confounding variables like socioeconomic status, air quality, and lifestyle factors, the predominance of correlational data from prospective cohort studies still constrains the ability to establish causation. These studies, while insightful, often struggle to fully untangle the intricate relationships between greenspace exposure and health outcomes, and may not comprehensively address all potential confounding factors.

To address these limitations, future research should aim for more standardised and nuanced metrics of greenspace exposure. This includes integrating detailed geospatial analyses and user surveys to better capture the quality and accessibility of greenspaces. Longitudinal studies and experimental designs could provide stronger evidence of causation and clarify the mechanisms underlying the observed effects. Additionally, research should explore molecular and cellular mechanisms that could elucidate how greenspace exposure impacts brain health. For instance, understanding how greenspaces influence neuroinflammation, oxidative stress, and neuroplasticity at the cellular level could provide insights into the biological pathways through which environmental factors affect cognitive function. A comprehensive approach incorporating detailed environmental assessments and individual health data will offer a more holistic view of the impacts of greenspaces on brain health.

By overcoming these methodological challenges, researchers can gain more precise insights into the complex relationships between greenspaces and health outcomes. Such advancements will not only deepen our understanding of greenspaces’ benefits but also inform more effective urban planning and public health strategies. This will support the development of targeted interventions aimed at optimising health and well-being through environmental design. The growing body of evidence highlights the potential of greenspaces as a crucial component in enhancing cognitive function and overall health, emphasising the need for continued refinement in research methodologies and addressing existing gaps to fully realise their benefits.