Lead exposure raises risk of ADHD

13:46, February 04, 2010      

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Kids with higher levels of lead may face greater risk of developing attention-deficit hyperactivity disorder (ADHD), U.S. researchers suggest.

Researchers at Oregon Health & Science University in Portland determined the link between lead and ADHD in two studies.

The first study 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, said Joel Nigg, a psychological scientist at the university.

In his article, published in the Feb. issue of Current Directions in Psychological Science, Nigg offers a causal model in which lead attaches to sites in the brain's striatum and frontal cortex, and acts on the genes in these regions -- causing them to turn on or remain inactive.

He said lead might disrupt brain activity in a way that leads to hyperactivity and attention problems.

Genes are believed to account for as much as 70 percent of ADHD in children. As for the other 30 percent, lead may be a prime suspect among possible environmental causes, according to the American Association of Psychological Science.

Nearly all children in the United States have measurable levels of lead in their bodies, the association reports.

Lead, a neurotoxin, is present in trace amounts in such things as soil, drinking water, children's costume jewelry and imported candies.

Source: Xinhua
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