Greenness Around Schools May Lower Risk of ADHD Symptoms

New research supports a correlation between living in greener areas and numerous improved health outcomes, attributed to factors such as reduced air pollution and noise, higher levels of physical activity, mitigated stress levels, and enriched microbial diversity.

Epidemiological studies examining greenness and attention-deficit/hyperactivity disorder (ADHD) or its symptoms have had conflicting conclusions. Previous studies largely focused on residential greenness, despite the fact that children spend significant portions of their day at school. Therefore, this study assessed the correlation between greenness surrounding schools or kindergartens and ADHD symptoms in children. The study was conducted between April 2012 and January 2013 and spanned seven cities in northeastern China.

A total of 59,754 children aged two to 17 years from 94 schools and kindergartens were included. Children were eligible for inclusion if they had lived in the study area for at least two years. The exposure—greenness surrounding the school or kindergarten—was determined per the normalized difference vegetation index and the soil-adjusted vegetation index. ADHD symptoms (nine each of inattention and hyperactivity-impulsivity symptoms) were measured per the Diagnostic and Statistical Manual of Mental Disorders (Fourth Edition) scales. The frequency of each symptom was reported by the parents or guardians during the six months preceding the study period. Children with at least six of the symptoms were considered to have ADHD.

The mean age of the children in the study was 10.3 years, and 49.4% were girls. Greenness levels differed greatly among schools and kindergartens; the normalized difference vegetation index within 500 m of an institution varied from –0.09 to 0.77. Children attending schools or kindergartens with higher levels of greenness were less likely to have ADHD symptoms. Covariate-adjusted models concluded that each 0.1-unit increase in normalized difference vegetation index or soil-adjusted vegetation index within 500 m of a school or kindergarten significantly reduced the risk of ADHD symptoms (odds ratios, 0.87 and 0.80, respectively).