A new international study has found no solid link between prenatal exposure to air pollution and an increased risk for attention-deficit/hyperactivity disorder (ADHD) symptoms in children aged 3 to 10 years.

The research, published in the journal Epidemiology, was led by the Barcelona Institute for Global Health (ISGlobal) and included data on nearly 30,000 children from seven European countries.

ADHD is the most common childhood behavioral disorder, affecting around 5 percent of children worldwide. It is characterized by a pattern of inattention, hyperactivity and/or impulsivity that is atypical for the child’s age. ADHD symptoms can interfere with development and have been linked to academic problems in school-aged children as well as an increased risk of problems with addiction or risky behaviors.

Although recent studies have shown that prenatal exposure to air pollution can impact children’s brain development, it has remained unclear whether air pollution can increase the risk of ADHD symptoms.

“Our findings show no association between exposure to air pollution during pregnancy and increased risk of ADHD symptoms,” said Dr. Joan Forns, lead author of the study.

The new study, which forms part of the European Study of Cohorts for Air Pollution Effects (ESCAPE), involved 30,000 children between 3 and 10 years of age from eight birth cohorts in Germany, Denmark, France, Italy, the Netherlands, Sweden and Spain (the latter consisting of four sub-cohorts from the INMA project in Gipuzkoa, Granada, Sabadell and Valencia).

For the study, the researchers estimated exposures to nitrogen oxides and particulate matter throughout pregnancy at each participant’s home address. ADHD symptoms were assessed using various questionnaires that had been filled out by parents and/or teachers.

“Given the conclusions of this study and the inconsistent findings of previous studies, we hypothesise that exposure to air pollution might not increase the risk of ADHD in children in the general population,” explained ISGlobal researcher Dr. Mònica Guxens, who coordinated the study.

“However, we believe that exposure to air pollution could have harmful effects on neuropsychological development, especially in genetically susceptible children.”

It has been shown that ADHD is the result of complex interactions between genetic background (heritability is approximately 75 percent), environmental factors and social determinants.

“We will continue to study the role of air pollution in order to rule out its association with childhood ADHD and improve our understanding of what causes this disorder,” said Guxens.

Source: Barcelona Institute for Global Health (ISGlobal)