Brain connection lies behind ADHD

New research indicates a connection in the brain might be responsible for causing attention deficit-hyperactivity disorder, or ADHD.

ADHD is one of the most prevalent mental disorders in children and teens and can last beyond adolescence. Its symptoms vary widely and can impair a person's ability to pay attention, complete a task or be productive.

"It is estimated that at least 3 to 5 percent of the adult population in the U.S. suffers from ADHD," said Dr. Nora Volkow, with the National Institute on Drug Abuse.

Past research has shown that symptoms like impulsive behavior and inattention could be caused by the disrupted transmission of dopamine, a chemical that helps cells communicate.

"Dopamine is considered a neurotransmitter that is crucial for our ability to perceive rewards and to be motivated in our behavior," Volkow said.

Published in the Journal of the American Medical Association, the study compared the dopamine reward pathway in the brains of 53 adults with ADHD and 44 adults who don't  have it.

"There was a lower concentration of dopamine markers in the brains of individuals with ADHD, specifically in the areas of the brain that are involved with reward and motivation," Volkow said.

Researchers said the findings help explain why ADHD have a hard time focusing on tasks they don't find interesting. The study supports the concept that making school and work tasks seem more rewarding to patients with ADHD could improve performance.