Extensive international research published on British Medical Journal highlighted how the greenery of cities can significantly contribute to improving the mental health of the population. The study, among the most complete ever carried out on the topic, suggests that an urban environment rich in nature is not only more pleasant, but represents a real protective factor against some psychological disorders.
The researchers’ work is based on over 11 million hospital admissions for mental health problems recorded between 2000 and 2019 in 7,000 cities spread across seven countries: Australia, Brazil, Canada, Chile, New Zealand, South Korea and Thailand. To measure the presence of greenery, scientists used the NDVI, an index obtained through satellite analysis capable of distinguishing areas without vegetation from areas with moderate or intense vegetation cover.
Not just a reduction in hospitalizations for mental disorders
A clear correlation emerges from the survey: even a modest increase in the vegetation index is associated with a 7% reduction in the overall risk of hospitalization for mental disorders. Some pathologies show even more marked effects: substance use disorders recorded a decline of 9%, psychotic disorders by 7%, dementia by 6% and anxiety by 3%. The impact is particularly evident in large metropolises, where an improvement in green coverage can lead to a reduction in risk of up to 13%.
Differences between countries and limitations of the study
The effects are not uniform everywhere: Thailand shows the most significant benefits, while in Australia the association appears less strong. The reasons can be many and include cultural, climatic, urban planning and differences in the management of health systems.
The authors of the survey also highlight some limitations: the study only concerns hospital admissions, excluding less serious cases, and the NDVI measures the quantity of vegetation, not its quality, accessibility or biodiversity, elements which could further influence psychological well-being.
Despite the limitations, the message is clear: investing in urban green spaces, accessible parks and ecological corridors not only brings aesthetic or environmental benefits, but can reduce pressure on the healthcare system, support productivity and improve collective well-being. Nature, in cities, is therefore confirmed not as a luxury, but as an essential resource.
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