Summary: Children who grew up in residential areas surrounded by green space were less likely to be diagnosed with ADHD than those who were raised in areas without access to nature.
Source: Aarhus University
The amount of green space surrounding children’s homes could be important for their risk of developing ADHD. This is shown by new research results from iPSYCH.
A team of researchers from Aarhus University has studied how green space around the residence affects the risk of children and adolescents being diagnosed with ADHD. And the researchers find an association.
“Our findings show that children who have been exposed to less green surroundings in their residential area in early childhood, which we define as lasting up until age five, have an increased risk of receiving an ADHD diagnosis when compared to children who have been surrounded by the highest level of green space,” says Malene Thygesen, who is one of the researchers behind the study.
ADHD is one of the most common psychiatric diagnoses among children and it affects those with the disorder in different ways. The reason why some children develop ADHD is still not fully known. ADHD may be hereditary, but other factors may also play a role. For this reason, there are strong arguments for research into the causes of children developing the diagnosis. One condition which has been of interest for research is children’s access to green space, as previous studies have found an association with children’s mental well-being and cognitive development.
A complete study
A single study does not provide sufficient basis to conclude that there exists an association between access to green environments and children’s risk of developing ADHD, as this requires further studies. But the results of Malene Thygesen and the team’s research are the same as those of previous similar research projects, and the study’s research methods have taken into account many of the other factors which can also come into play in the development of ADHD.
“In the study we adjusted for gender, age, the child’s year of birth, and the parents’ psychiatric diagnosis and socio-economic status, and neighborhood level socio-economic status. Our study is strong because it includes many individuals and because the information is very detailed. For example, we use data based on clinical diagnoses of ADHD made by specialists,” says Malene Thygesen.
Perspectives for further research
The research article written on the basis of this study can be found in the journal Environmental Health Perspectives and may inspire researchers to continue studying the association between access to green spaces and the risk of children being diagnosed with ADHD or other diagnoses.
“It’s interesting to think that living in green environments may be a protective factor for children in relation to the risk of developing ADHD.”Methodology
The study makes use of data on the addresses of more than 800,000 people born from 1992 and up until 2007, as well as information on clinical ADHD diagnoses from age five until 2016. In addition, the researchers use a specific measurement of how green the environment around a household is, the so-called normalized differential vegetation index. This measurement places the address in the middle of a quadratic area with 210 meters on each side, and on this basis calculates how green the surrounding area is.
About this ADHD research news
Source: Aarhus University Contact: Press Office – Aarhus University Image: The image is in the public domain
The Association between Residential Green Space in Childhood and Development of Attention Deficit Hyperactivity Disorder: A Population-Based Cohort Study
Access to green space has been hypothesized to have a beneficial impact on children’s mental well-being and cognitive development. The underlying mechanisms of the mental health benefits of green space are not fully understood, but different pathways have been suggested, such as the psychologically restoring capacities of green space, the ability to facilitate physical activity and social cohesion, and the mitigation of exposure to air pollution.
In this nationwide cohort study, we investigated associations between residential green space in early childhood and a clinical diagnosis of attention deficit hyperactivity disorder (ADHD).
The cohort included individuals, who were born in Denmark between 1992 and 2007 (n=814,689n=814,689) and followed for a diagnosis of ADHD from age 5, during the period 1997–2016. We used the normalized difference vegetation index (NDVI) as a measure of vegetation greenness surrounding each residential address in a quadratic area of 210m×210m210m×210m in which the residence was located in the center of the quadrate. Individual exposure to green space was calculated as the average of NDVI surrounding each individual’s residential address (or addresses if more than one) between birth and the fifth birthday. Multilevel modeling was used to estimate the incidence rate ratios (IRRs) with 95% confidence intervals (CI) for ADHD, according to exposure level and adjusted for calendar time, age, sex, parental socioeconomic status, neighborhood level socioeconomic status, and urbanicity.
Individuals living in areas defined by sparse green vegetation (lowest decile of NDVI) had an increased risk of developing ADHD, compared with individuals living in areas within the highest decile of NDVI (IRR=1.55IRR=1.55; 95% CI: 1.46, 1.65). Adjusting for the known confounders attenuated the result, but the association remained (IRR=1.20IRR=1.20; 95% CI: 1.13, 1.28).
Our findings suggest that lower levels of green space in residential surroundings, during early childhood, may be associated with a higher risk of developing ADHD.