Lead and tobacco exposure seem to raise risks.
THE QUESTION Might exposure to lead and tobacco be linked to the development of attention-deficit/hyperactivity disorder (ADHD)?
THIS STUDY analyzed data on 2,588 children, 8 to 15 years old from across the United States; 222 of them had ADHD. Children whose mothers had smoked while pregnant were more than twice as likely to have ADHD as children whose mothers did not smoke. Essentially no difference was found, however, between children who did and did not live with smokers at the time of the study. Children who had the highest levels of lead in their blood also had double the risk for ADHD, compared with those with the lowest blood levels of lead. When combined, prenatal exposure to tobacco and high childhood levels of lead in the blood increased the likelihood of ADHD eightfold over children with no tobacco exposure and the lowest lead levels.
WHO MAY BE AFFECTED? Children. About 5 million children in the United States have been diagnosed with ADHD, a condition associated with difficulty paying attention and controlling impulsive behavior. Although genetics are believed to be involved in the presence of ADHD, some also think that environmental factors might play a role in the disorder.
CAVEATS Data on smoking came from the mothers' answers on a questionnaire and did not include the number of cigarettes smoked. The study found a link between tobacco, lead and ADHD but did not prove that the factors caused the disorder.
FIND THIS STUDY Nov. 23 online issue of Pediatrics.