Early exposure to smoke, lead increase ADHD risk

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Prenatal exposure to tobacco, coupled with lead exposure in infancy and early childhood can dramatically increase the risk for Attention Deficit Hyperactivity Disorder (ADHD) in children, according to research published online today in the journal Pediatrics. Together these environmental factors can increase a child’s risk for ADHD by 8%, researchers conclude. By eliminating these exposures during pregnancy and early childhood, parents could help reduce ADHD cases by as much as 35%—or roughly 800,000 kids—the researchers estimate.

The study, led by Dr. Tanya Froehlich from the Division of Developmental and Behavioral Pediatrics at Cincinnati Children’s Hospital, analyzed the impact of prenatal tobacco exposure and early lead exposure on the development of ADHD among nearly 3,000 children between the ages of 8 and 15. Tobacco exposure was assessed by surveying parents and caregivers about the mother’s smoking habits during pregnancy; blood tests administered during the course of the study were used to measure lead exposure. ADHD diagnoses were confirmed by asking caregivers if children had been previously told by a physician that they had ADHD, treated for the disorder with medication, and by completing diagnostic interviews based on criteria from the current Diagnostic and Statistical Manual of Mental Disorders. (Nearly 9% of the children in the study met the diagnostic criteria for ADHD.)

The researchers found that, not only did lead and tobacco exposures together increase the risk for ADHD, but they also presented increased risk independently. Compared to peers without exposure to either substance, children exposed to tobacco smoke in utero were 2.4 times more likely to have ADHD, and those whose blood tests indicated lead exposure during infancy and early childhood were 2.3 times more likely to have ADHD.

While currently most ADHD research is focused on building effective treatments for the disorder, these findings suggest that efforts toward prevention may have a powerful impact as well.