Finding the cause of ADHD

September 8, 2009 3:19:36 PM PDT
Attention deficit-hyperactivity disorder, or ADHD, is one of the most prevalent mental disorders in children and teens. And it can also continue way past adolescence.But now, new research could bring doctors closer to finding the cause of it.

ADHD symptoms vary widely and can impair a person's ability to pay attention, complete tasks and be productive. The new research looks at how a faulty neurotransmission in the brain and our responses to reward may be at the root of some of these issues. Approximately 3 to 5 percent of Americans have ADHD.

Many of the adults and children with ADHD have trouble completing tasks when there is no immediate reward on the horizon. But interestingly, they are able to pay attention at other times.

That may be because of a disruption in a brain chemical called dopamine.

Dopamine helps cells to communicate, and researchers believe that a disruption in the transmission of dopamine may actually be the reason many patients struggle to complete tasks when there's no immediate reward.

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

Dr. Volkow and her colleagues compared what is called the dopamine reward pathway in the brains of 53 adults who had ADHD with 44 adults who did not, using images taken at Brookhaven National Laboratory on Long Island.

Their findings confirmed what they suspected.

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

While the findings are preliminary and need to be duplicated, the researchers say they may help explain why ADHD patients have such a hard time focusing on tasks they don't find interesting. It's not that they don't want to, but their brains are directing them otherwise. The study reinforces the concept of how creating ways to make school and work tasks seem more rewarding to patients with ADHD could result in improved performance.

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