A study led by the Vall d'Hebron Research Institute (VHIR) and the Sant Joan de Déu Research Institute (IRSJD) shows the effects of air pollution and green spaces on the development of emotional and behavioural problems in children and adolescents in Catalonia. The study, published in the journal Child and Adolescent Mental Health, has been made possible thanks to the support of La Marató de 3Cat and the Mental Health area of the CIBER (CIBERSAM) and the collaboration with the Barcelona Institute for Global Health (ISGlobal), centre promoted by the "la Caixa" Foundation.

Emotional and behavioural problems are common in childhood: an estimated 13.4% of children and adolescents worldwide suffer from mental health problems. These disorders can persist into adulthood and have a major impact on individuals and their families. Although genetics is important, the role of environmental factors in the development of mental health is widely accepted. In this regard, there is growing evidence that physical environmental factors present in the environment also play a key role in brain health.

Among the environmental factors that can affect the brain is environmental pollution. "So far there are many studies conducted in adults, but it is essential to study these effects in childhood, as it is a key stage of development and can have long-term consequences", explains Dr. Silvia Alemany, principal investigator of the Psychiatry, Mental Health and Addictions group at VHIR and CIBERSAM.

To better understand the relationship between the environment and mental health in childhood, the VHIR and the IRSJD have coordinated a study with 4,485 children and adolescents from 48 schools and institutes in Catalonia, both public and private. On the one hand, they studied their exposure to several air pollutants, such as nitrogen dioxide and particulate matter, as well as the proximity of green spaces to schools. On the other hand, the mental health of each child was analysed through family questionnaires. The effects of exposure to pollution and proximity to green spaces were studied for periods between one and four years prior to the assessment of emotional and behavioural problems.

The results showed that exposure to air pollution, especially PM10, is associated with an increased risk of emotional problems such as anxiety and depression, effects that were observed after one year.

On the other hand, having green areas within 100 metres of the school was found to reduce children's aggressive behaviour. These differences were observed even four years after exposure. The research team points out that this may be due to beneficial effects derived directly from exposure to green spaces, such as reduced stress levels, or through other mechanisms such as the promotion of physical activity, social interaction, free play, or a reduction in noise or pollution.

The paper also looked at whether gender, age, socioeconomic status or genetic predisposition might influence these outcomes. No significant differences were found, indicating that these effects occur independently of these factors.

Improving air quality for the benefit of mental health

The results of this study highlight the need to reduce pollution and increase green spaces to protect children's mental health. "Strategies to improve air quality and increase green spaces are needed, especially in areas near schools", says Dr. Rosa Bosch, coordinator of the SJD MIND Schools programme at the IRSJD, member of CIBERSAM, Head of Research at the Mental Health Division of Althaia Red Asistencial Universitaria de Manresa, and co-first author of the study.

In the future, it is essential to continue to study in depth the relationship between pollution and children's mental health in order to develop more effective measures to promote health.

Exposure to pollutants is a daily problem for a large proportion of the population. For this reason, "even small changes in exposures can translate into improvements in the quality of life of many families in the short and long term", says Uxue Zubizarreta-Arruti, predoctoral researcher in the Psychiatry, Mental Health and Addictions group at VHIR and co-first author of the study.

The work has been made possible thanks to funding from other entities such as the Agency for the Management of University and Research Grants (AGAUR), the Carlos III Health Institute, La Marató de 3Cat, the European Regional Development Foundation (ERDF), the ECNP Network ‘ADHD across the Lifespan’, the Fundació ‘la Caixa’, the Diputació de Barcelona, the ‘Pla Estratègic de Recerca i Innovació en Salut’ (PERIS), the Fundació Privada d'Investigació Sant Pau (FISP) and the Department of Health of the Generalitat de Catalunya.