Objectives: Attention deficit hyperactivity disorder (ADHD) is the most frequently diagnosed neurobehavioral disorder of childhood, yet its etiology is not well understood. In this article we present evidence that environmental chemicals, particularly polychlorinated biphenyls (PCBs) and lead, are associated with deficits in many neurobehavioral functions that are also impaired in ADHD.

Data Sources: Human and animal studies of developmental PCB or lead exposure that assessed specific functional domains shown to be impaired in ADHD children were identified via searches of PubMed using lead or PCB exposure in combination with keywords including attention, working memory, response inhibition, executive function, cognitive function, behavior and ADHD.

Data Synthesis: Children and laboratory animals exposed to lead or PCBs show deficits in many aspects of attention and executive function that have been shown to be impaired in children diagnosed with ADHD, including tests of working memory, response inhibition, vigilance and alertness. Studies conducted to date suggest that lead may impact both attention and response inhibition, whereas PCBs may impair response inhibition to a greater degree than attention. Low level lead exposure has been associated with a clinical diagnosis of ADHD in several recent studies. Similar studies of PCBs have not been conducted.

Conclusions: We speculate that exposures to environmental contaminants including lead and PCBs may increase the prevalence of ADHD.

Source: Techcombo