Trees improve children’s mental health

Everyone knows that trees clean the air, but now scientists say they might even clear the mind. John Dyer reports.

Image credit: Jenn Evelyn-Ann via Unsplash

Children who grow up around trees, grass, bushes and other greenery are more mentally resilient later in life, according to new research from Aarhus University in Denmark.

“With our dataset, we show that the risk of developing a mental disorder decreases incrementally the longer you have been surrounded by green space from birth and up to the age of 10,” said study lead author Kristine Engemann, a postdoctoral researcher at the university’s Department of Bioscience and the National Centre for Register-based Research, in a press release.

“Green space throughout childhood is therefore extremely important.”

Greater risk for depression without green spaces

Engemann and her colleagues found that children who grow up without green surroundings face a 15 to 55 per cent greater chance of developing depression and other mental disorders later in life. That percentage was adjusted to account for family histories, urbanization and socio-economic status.

The study found, for example, that a lack of green space was correlated to higher rates of alcoholism. But they found no association with intellectual disabilities and the absence or presence of green space.

Publishing their research in the journal Proceedings of the National Academy of Sciences, the scientists used satellite date from 1985 to 2013, mapping green space around the homes of one million Danes and cross referencing that data with 16 mental disorders discovered in the same geographic locations.

They used the Danish Civil Registration System, a system created in 1968 that tracks every Danish citizen’s gender, place of birth, residence, health records and parent’s information. Around a fifth of Danish adults suffer from poor psychiatric health annually. The World Economic Forum said that more than 87 per cent of Danes lived in cities.

Massive amount of data

“Our data is unique,” said Engemann. “We have had the opportunity to use a massive amount of data from Danish registers of, among other things, residential location and disease diagnoses and compare it with satellite images revealing the extent of green space surrounding each individual when growing up.”

Scholars who were not affiliated with the study corroborated Engemann’s claims.

“The scale of this study is quite something,” said Kelly Lambert, a University of Richmond neuroscientist, speaking to National Public Radio.

Urban settings linked to mental disorders

Other studies have found more instances of schizophrenia, mood disorders and cognitive development issues among people who live in settings of concrete and steel.

The findings build on science that demonstrates that environmental factors common to cities – noise, air pollution, infections and poor socio-economic condition – make mental disorders more likely. Green spaces in urban settings also cultivate more social interactions between people, boost exercise and help children’s cognitive development, research has found.

“There is increasing evidence that the natural environment plays a larger role for mental health than previously thought,” said Engemann. “Our study is important in giving us a better understanding of its importance across the broader population.”

The data did not distinguish between parks, old-growth forests, overgrown lots in cities and other types of greenery, suggesting the researchers had more work to do to narrow the lessons of their inquiries.

Implications for urban planning

But it was clear the research has important implications for the future, the scientists added, noting that more people are living in cramped cities that lack greenery. At the same time, mental disorders have been rising. Around 450 million people from mental disorders worldwide, according to the World Health Organization.

“The coupling between mental health and access to green space in your local area is something that should be considered even more in urban planning to ensure greener and healthier cities and improve mental health of urban residents in the future,” said study co-author Jens-Christian Svenning, a professor of ecology at Aarhus University.

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