Being denied the sights, sounds and smells of nature during childhood is associated with an increased risk of mental health problems later in life, according to a new study.

Scientists at Aarhus University in Denmark studied data on 1 million Danes born between 1985 and 2003. They found that growing up deprived of green space is associated with an up to 55% higher risk of mental illness.

Back to nature

The survey used satellite data from as far back as the 1980s to calculate the vegetation density around each participant’s dwelling.

After establishing the greenery factor of each childhood residence, the researchers screened the adult participants for 16 different mental health disorders.

At this stage they had to overcome a few challenges.

From the satellite data, they were able to determine vegetation density, but found it difficult to distinguish between different types of green spaces, which made it unclear if parks or heathland were more beneficial for mental health than fields or forests, for example.

Researchers calculated the vegetation density around each childhood home.
Image: PNAS

The study also had to adjust for the impact of external factors, such as urbanization, socioeconomic factors, family history of mental illness, and parental age. But fortunately the researchers had access to the Danish Civil Registration System, which contained a wealth of data on each participant.

The results showed that greater exposure to green spaces during childhood lowered the risk of psychiatric disorders in adulthood by between 15% and 55%, depending on the type of disorder. For example, there was a strong association with lack of green space and alcoholism, but no association with intellectual disabilities.

Children growing up in an urban environment surrounded by trees, plants and grass were found to be less prone to developing mental health issues in later life than those from rural or less green urban environments.

Urban jungle

While the study didn’t establish the reasons for the association, the researchers said their results were consistent with other work showing better mental well-being and cognitive development among children with access to more green space.

“These findings contribute to our understanding of the urban environment as an important environmental risk factor for mental health and can guide the design of healthy city environments, as well as institutions and programs affecting childhood life, for example, school systems,” they wrote.

Image: Statista

As the chart shows, a high proportion of Denmark’s population live in towns and cities, a share which is steadily increasing over time. In 2017, more than 87% of Danes called an urban area home.

Urbanization in Denmark is part of a broader global trend of people moving from rural to urban areas. Currently, cities are home to half the world’s population, and the United Nations predicts that figure will grow to 68% by 2050.

To accommodate new residents, cities are expanding rapidly, which in turn puts pressure on green spaces. But as urban populations – and the stresses and strains of city living – grow, we will need them more than ever.