TUESDAY, Feb. 2, 2010 (HealthDay News) -- Lead may play a role in the development of attention-deficit hyperactivity disorder (ADHD), new research suggests.
Genes are believed to account for as much as 70 percent of ADHD in children. Researchers trying to determine the cause of the other 30 percent of cases consider lead a prime suspect among possible environmental causes, according to the American Association of Psychological Science.
Lead, a neurotoxin, is present in trace amounts in such things as soil, drinking water, children's costume jewelry and imported candies. Nearly all children in the United States have measurable levels of lead in their bodies, the association reports.
In one of two recent studies examining the possible link between lead and ADHD, the researchers found that children with ADHD had slightly higher levels of lead in their blood than did children without ADHD. The second study showed an association between elevated levels of lead in children's blood and parent/teacher ratings of ADHD symptoms, including both hyperactivity and attention problems.
In both studies, the link between lead and ADHD was independent of the children's IQ, family income, race or whether their mothers had smoked during pregnancy.
The findings strongly suggest that lead may be a cause of ADHD, according to Joel Nigg, a psychological scientist at Oregon Health & Science University. He said that lead might disrupt brain activity in a way that leads to hyperactivity and attention problems.
The studies are published in the February issue of the journal Current Directions in Psychological Science.
The U.S. National Institute of Mental Health has more about ADHD.