Exploring the pathways linking prenatal and early childhood greenness exposure to attention-deficit/hyperactivity disorder symptoms during childhood: An approach based on robust causal inference

• Published in: International journal of hygiene and environmental health 2025-01, Vol.263, p.114475, Article 114475
• Main Authors: Luque-García, Leire, García-Baquero, Gonzalo, Lertxundi, Aitana, Al-Delaimy, Wael K., Julvez, Jordi, Estarlich, Marisa, De Castro, Montserrat, Guxens, Mònica, Lozano, Manuel, Subiza-Pérez, Mikel, Ibarluzea, Jesús
• Format: Article
• Language: English
• Subjects: ADHD; Air Pollutants - analysis; Air pollution; Attention Deficit Disorder with Hyperactivity - epidemiology; Child; Child, Preschool; Children; Environmental Exposure - adverse effects; Exercise; Female; Green space; Humans; Infant; Male; Particulate Matter - analysis; Physical activity; Pregnancy; Prenatal Exposure Delayed Effects - epidemiology; Prospective Studies; Urban environment
• ISSN: 1438-4639; 1618-131X; 1618-131X
• DOI: 10.1016/j.ijheh.2024.114475

Epidemiological studies suggest that exposure to greenness during childhood may protect children from developing attention-deficit hyperactivity disorder (ADHD). We analyzed the effect of both prenatal (pregnancy) and early childhood (4-5-year follow-up) residential greenness exposure and green space availability on ADHD symptoms during childhood (up to the age of 12 years) and further explored the potential mediating role of PM2.5 and physical activity in the association. The study population included participants from the INfancia y Medio Ambiente (INMA) prospective birth cohort (Gipuzkoa, Sabadell, and Valencia). Average Normalized Difference Vegetation Index (NDVI) in buffers of 100-, 300- and 500-m around the residential addresses was used as an indicator of greenness, while green space availability was determined based on the presence of a major green space within 150-m from the residence. Childhood ADHD symptoms were assessed at the 6-8- and 10-12-year follow-ups using Conners Parents Rating Scale-Revised: Short Form. Although no association was found for the prenatal exposure period, increased early childhood NDVI inversely associated with the OR of clinically significant ADHD symptoms during the 6-8-year follow-up at the 100-m (OR 0.03, 95% CI: 0.003 to 0.44), 300-m (OR 0.04, 95% CI: 0.003 to 0.42) and 500-m (OR 0.08, 95% CI: 0.01 to 0.76) buffers, but exclusively in the context of direct effects. Additionally, the 10-12-year follow-up analysis found moderate to weak evidence of potential total and direct effects of NDVI at both 100- and 300-m buffers on inattention scores, as well as for NDVI at the 300-m buffer on ADHD index scores. The analysis did not reveal evidence of mediation through PM2.5 or physical activity. The evidence suggests that early childhood greenness exposure may reduce the risk of developing ADHD symptoms later in childhood, and that this association is not mediated through PM2.5 and physical activity. •Analyzed greenness exposure independently across pregnancy and early childhood.•Prenatal greenness was not associated with ADHD symptoms.•The study identified evidence suggestive of a protective effect for early childhood greenness.•There was no evidence of mediation through PM2.5 or physical activity.