Lead may be ADHD trigger

PORTLAND, Ore., Jan. 29 (UPI) -- A U.S. researcher says attention-deficit hyperactivity disorder may be linked to the neurotoxin lead -- still found in some toys, jewelry and water.

Joel Nigg of Oregon Health & Science University in Portland points to lead as an ideal candidate to trigger the developmental disorder called ADHD.

In his article, published in 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. This disruption in brain activity alters cognitive control, and in turn results in hyperactivity and lack of vigilance.

Two recent studies, Nigg says, provide strong evidence of the link between ADHD and lead. One found children who had been diagnosed with ADHD had slightly higher levels of lead in their blood than healthy controls.

The second study shows a link between blood lead and both parent and teacher ratings of ADHD symptoms, including both hyperactivity and attention problems. In both studies, the connection was independent of IQ, family income, race or maternal smoking during pregnancy.