Differences Found in Hyperactive Kids’ Brains

Stanford researchers have found the first clear difference in brain functioning between children with attention deficit hyperactivity disorder (ADHD) and healthy children, a discovery that may lead to more objective ways to diagnose this mysterious brain malfunction.

Researchers estimate that as many as 6% of school-age children suffer from ADHD and require medication with Ritalin to allow them to function properly. Critics, however, charge that the drug is widely overprescribed and is routinely given to children who are merely exuberant, not hyperactive.

In the absence of an objective way to diagnose the disorder, this controversy probably will continue. If the new findings hold up under further study, however, they offer hope for ending that dispute.

Using a non-intrusive technique called functional magnetic resonance imaging, psychologist John Gabrieli and his colleagues at Stanford were able to show that specific areas of the brain called the basal ganglia are less active in ADHD children than in healthy ones.

They also found the first evidence that Ritalin works differently in children with ADHD, a finding that may lead to the first explanation of why a stimulant seems to have calming properties.

Their studies show that Ritalin increases brain activity in the basal ganglia in hyperactive children, but decreases basal ganglia activity in healthy children, the team reports in today’s Proceedings of the National Academy of Sciences.

The Stanford team studied only 16 children and the results need to be replicated, said Dr. F. Xavier Castellanos of the National Institute of Mental Health, but it potentially offers the first objective means of diagnosing the disorder.

The finding comes only a few days after a conference at the National Institutes of Health concluded that an objective means of diagnosing the disorder is urgently needed.

“There’s a lot we have to understand yet, but this is a good first start,” Castellanos said.

“We will always have to use behavioral observations in diagnosing ADHD, but this will potentially give us a good way to distinguish it from other problems, such as learning disorders and early-onset bipolar disorder,” said Dr. Julie Schweitzer of the Emory University School of Medicine in Atlanta.

Children diagnosed with ADHD exhibit a series of problems, including inattentiveness, poor listening skills, failure to follow directions and the inability to control impulses. Many of those problems are carried through into adult behavior.

For 30 years, the disorder has been treated with Ritalin, an amphetamine-like stimulant that, paradoxically, calms the children and increases their attentiveness.

The market research firm IMS Health says 13.9 million prescriptions for Ritalin and other stimulants were dispensed to children during the last school year, an 81.2% increase from the 7.7 million recorded five years earlier.

The American Medical Assn. reported recently that it found little evidence that Ritalin is overused, but critics say it is widely used to control students who merely misbehave in the classroom.

Looking for a new diagnostic tool, Gabrieli and his colleagues studied 16 boys between the ages of 8 and 13. Ten of them were diagnosed with ADHD, six were not.

The boys were asked to play a mental game while lying in a magnetic resonance imaging device focused on the front part of the brain. A series of random letters were flashed on a mirror visible to the boys and they were asked to press a button every time they saw a letter other than X.

Because X appeared infrequently, they developed a bias toward pressing the button. The theory was that boys with ADHD would have a harder time controlling the bias because of their poor impulse control, and that is what the researchers found.

All of the ADHD boys normally received Ritalin, but they were taken off it for a couple of days before the test.

Gabrieli and his colleagues found that the basal ganglia were less active in the boys with ADHD during the test.

Both groups of boys improved their performance on the test when they were administered Ritalin. But the drug increased activity of the basal ganglia in the ADHD boys and decreased it in the control group.

Gabrieli cautioned that they have yet to study girls or ADHD children who have never been exposed to Ritalin. He estimates that at least 200 children will have to be studied before physicians can begin to think about using the technique for diagnosis.