Gene variant linked to ADHD

Bethesda, Md. -- U.S. scientists have linked a variant of a dopamine receptor gene with attention-deficit/hyperactivity disorder, as well as with thinner brain tissue.

ADHD is among the most heritable of mental disorders. Several genes have been associated with the condition, and one of the most frequently cited is a type of dopamine receptor gene called DRD4.

Previous studies suggested carriers of DRD4 might have a unique neuropsychological, clinical and pharmacological profile.

Dr. Philip Shaw of the National Institute of Mental Health and colleagues compared 105 children with ADHD with 103 healthy controls -- using both magnetic resonance imaging and DNA testing -- and found those with DRD4, both with and without ADHD, had thinner tissue in areas of the brain known to control attention.

People with ADHD and the DRD4 gene had better clinical outcomes and regained thickness in their right parietal cortex -- a sign previously linked to better outcomes.

The scientists said previous studies linked cortical thickness with better memory and learning capacity.

"In children, gains in verbal knowledge are mirrored by change in the cortical thickness of speech areas," they said.

The study is reported in the August issue of Archives of General Psychiatry.

Copyright 2007 by United Press International.