Green spaces are declining
In a rapidly urbanizing world, green spaces are shrinking as cities grow larger. Scientists have been striving to understand how green spaces, or their absence, affects our mental health.
Researchers from Aarhus University in Denmark have found that growing up near vegetation is associated with a nearly 55 percent lower risk of mental health disorders in adulthood. A biologist who led the study merged decades of satellite imagery with extensive health and demographic data about the Danish population to investigate the mental health effects of growing up near greenery.
What studies show
According to the University of Richmond in Virginia, the scale of this study is unprecedented. Smaller studies have hinted that lack of green space increases the risk of mood disorders and schizophrenia and can even affect cognitive development.
However, factors like socioeconomic status, family history of mental illness, and urbanization can also have big effects on mental health. Wealthy families might be able to afford to live in neighborhoods with more access to nature and also have access to other resources that could enhance childhood development.
Satellite data extending back to 1985 allowed researchers to calculate vegetation density around residences. The data can't distinguish an old-growth forest from a large field, but in general, the more greenery a plot of land has, the higher the vegetation density. Researchers then compared the risk of developing various mental health disorders in adulthood with how much green space surrounded each residence. Since they had data for yearly income, work history, and education level, they could weigh the relative contribution of green spaces against socioeconomics of family and neighborhood.
After accounting for potential skewing factors, the researchers found that growing up near green space was associated with a 15-55% lower risk of developing psychiatric illness in adulthood, depending on the specific illness. Alcoholism was most strongly associated with lack of green space growing up. However, risk of developing an intellectual disability was not associated with green space.
The strength of the association between green space and the risk of psychiatric disorder was similar to other factors known to effect mental health such as socioeconomic status. It's estimated that about 20% of the adult Danish population will suffer from poor psychiatric health within any given year.
Green space appeared to have an association that was similar in strength to other influences such as a family history of mental health disorders or socioeconomic status. The effect of green space showed that the more childhood was spent in close proximity to greenery, the lower the risk of mental health problems in adulthood. One researcher said that he effect was remarkable. The results suggest that being able to go for a walk in the park as a kid is just as impactful. The greenery association with better mental health was the same in both rural and urban areas of Denmark. According to one researcher, "You could grow up in very urban areas but still have reduced risk if you're surrounded by green spaces". The study does not address how different kinds of green space or how it's used affects mental health.
Why does growing up near trees, shrubs and grass help limit mental health problems? Something about being exposed to the natural environment may have powerful physiological and psychological effects. More green space could encourage more social interaction, exercise, and a decrease of air and noise pollution. Exposure to a wider diversity of microbes in childhood could play a part. The studies suggest that something as simple as better city planning can have a profound impact on the mental health and well-being of everyone.