Nearly half a million cases of attention-deficit hyperactivity disorder among U.S. children are related to exposures to lead or their mothers' smoking while pregnant, a nationwide study suggests. The two environmental hazards might account for more than a quarter of drug-treated ADHD cases.
The finding bolsters earlier research that linked smoke exposure to ADHD and provides the best evidence yet that lead, a brain-damaging metal, might also contribute to the common behavioral disorder.
Published online on Sept. 19 for an upcoming Environmental Health Perspectives, the study analyzed data on 4,704 children who were 4 to 15 years old when they participated in a recent nationwide survey of health and nutrition.
Surveyors recorded that 4.2 percent of the children had been both diagnosed with ADHD and prescribed stimulants to treat the condition. The researchers collected other data as well, inc