Relationship of persistent organic pollutants to ADHD in children : a meta-analysis

Abstract

Attention deficit hyperactivity disorder (ADHD) is a brain-based disorder that causes a syndrome of behaviours in children and adults. People that have ADHD are hyperactive and inattentive so that their ability to concentrate on tasks is impaired, which often causes difficulty learning at school or on the jobsite. However, little research is available regarding the potential causes of ADHD, and while some sources identify environmental toxins as one of the potential factors, the results of the studies are contradictory and inconclusive. To address this issue, a meta-analysis was performed to explore the relationship between attention deficit hyperactivity disorder (ADHD) and exposure to persistent organic pollutants (POPs). Using meta-analysis of peer-reviewed articles from Science Direct, PubMed, PsychINFO, Scopus, ProQuest, and ERIC databases published in English since 2000, a relationship between POPs and ADHD is examined. Meta-analysis of twenty-one studies suggests a relationship between POPs and ADHD with a pooled odds ratio of 1.23 (95% CI [1.02, 1.48], p = 0.034). Sub-categories of toxins including polyaromatic hydrocarbons (PAHs), methylmercury, organochlorines, dioxins, polychlorinated biphenyls (PCBs), polybromodiphenyl ethers (PBDEs), perfluorinated compounds (PFCs), and phthalates are individually analysed; however, none of these can be shown to have a significant relationship to ADHD. Unfortunately, meta-analysis of the sub-categories is limited by the small number and heterogeneity of articles available within each sub-category. Still, the results suggest positive correlations between some of these particular toxins (e.g., PFCs) and the incidence of ADHD. Policy should be enacted to limit exposure to these substances, particularly exposure to the young.