New Study Zeros In on ADHD Cause

By Madeline Ellis

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It was in 1902 that physician George F. Still first documented what is now known as attention deficit/hyperactivity disorder (ADHD) , and despite more than a century of research, its exactcause is still not fully understood. Evidence to date indicates that there are many underlying factors that lead to the inattention, impulsiveness and hyperactivity seen in ADHD, among them genetic and neurobiological vulnerabilities, but the basic problem is thought to be in the disruption of certain neurotransmitters in the brain. Studies have shown that transmission of dopamine, a chemical needed for normal functioning of the central nervous system, is disrupted in some of the pathways of the brain in people with ADHD, and now researchers at the National Institute on Drug Abuse say they have pinpointed the areas in the brain where this seems to occur.

Using images taken at Brookhaven National Laboratory on Long Island, Dr. Nora Volkow and colleagues compared the brains of 53 adults with ADHD to 44 adults without the disorder. The researchers found that the brains of those with ADHD had a reduced concentration of dopamine receptors and transporters, specifically in the areas involved with reward and motivation, and this disruption “was directly related to the severity of inattention.”

This finding may explain why children and adults with ADHD have difficulty completing tasks when there is no immediate reward on the horizon, yet are able to concentrate when the activities are ones they enjoy or that come easy to them. The researchers say it may also explain why ADHD patients are prone to complications such as drug abuse and obesity. “This pathway plays a key role in reinforcement, motivation, and in learning how to associate various stimuli with rewards,” says Volkow.

Dr. Andrew Adesman, chief of developmental and behavioral pediatrics at Schneider Children’s Hospital in New York, agrees the study provides further support for the association between ADHD and dopamine deficits in specific areas of the mid-brain, but notes that “patients and professionals must recognize that, despite research advances identifying differences in the brains of patients with ADHD, the diagnosis of ADHD remains a clinical one,” Adesman said. “ADHD cannot be diagnosed by neuroimaging.”

Volkow says their results also lend credence to the continued use of stimulant medications in the treatment of ADHD, as they have been shown to target the dopamine pathway—enhancing motivation and increasing attention to cognitive tasks. But the findings should also serve as a “wake-up call for teachers,” she says. Knowing that the problem is one of motivation, teachers could devise ways of enhancing “the appeal and relevance of school” for these children. “It’s a great opportunity to develop curriculum that is much more exciting and engaging for kids suffering from ADHD.”

ADHD is the most commonly diagnosed childhood psychiatric disorder, estimated to affect three to seven percent of America’s children. On average, at least one child in every classroom in the United States needs help for the disorder.
However, more than half of ADHD children will continue to display characteristics of the disorder throughout adolescence and adulthood.

The study findings are reported in the September 9th issue of the Journal of the American Medical Association.

I thought this article was very interesting because it talks about in which areas of the brain ADHD has an effect on and how it affects them. By comparing ADHD patients with "normal" functioning adult brains they were able to distinguish the areas which are affected by ADHD. Attention deficit/hyperactivity disorder has been an important topic of discussion in the last several years because it has not been fully understood even though there are many who are affected by it. I also found really interesting that ADHD cannot be diagnosed by neuroimaging and as the article further explains; ADHD remains a clinical diagnosis and will stay that way.

David Figueroa

VTTP 434