Ground-breaking research linking attention-deficit disorder to a specific brain abnormality is expected to fuel the ongoing controversy over whether children with the disorder should be entitled to special-education services.
Researchers at the National Institute of Mental Health have found that, in the brains of adults who have the disorder, glucose is metabolized at significantly lower rates than it is in other adults. The findings were published Nov. 15 in the New England Journal of Medicine.
Researchers and advocates for children with attention deficits said the study is significant for two reasons: It adds to a growing body of evidence indicating the disorder has a unique biological base, and it holds out some promise that a diagnostic test for attention-deficit disorder will one day be developed.
“It seems inevitable now that schools will have to take some responsibility for the special needs of these children just as they do for other children with handicaps,” said C. Keith Conners, who directs the attention-deficit-disorders program at Duke University’s school of medicine.
An estimated 2 percent to 4 percent of all children suffer from the disorder, also referred to as attention deficit-hyperactivity disorder, or hyperactivity. It is often characterized in children by extreme fidgetiness, impulsivity, and an inability to concentrate. Studies have shown that children with the disorder suffer in school because they are often in trouble with their teachers and unpopular with their peers.
While low doses of amphetamines can control the disorder in many children, some hyperactive children also need behavior-management therapies or other special-education interventions to succeed in school.
But parents and advocates for those children have long contended that schools are either refusing to provide them those kinds of services or are serving them inappropriately under another special-education category, such as learning-disabled.
In an attempt to assure that their children have access to the right kinds of services in school, those groups lobbied the Congress earlier this year to expand the federal definition of eligible special-education categories to include the disorder. (See Education Week, Sept. 5, 1990.)
That effort failed when it ran into heated opposition from a wide range of education and civil-rights groups. Advocates have vowed to take up their campaign again next year.
“Finally, there’s going to be recognition that this is not simply bad parenting,” Sandra F. Thomas, president of Children with Attention Deficit Disorder, a support group for parents, said of the study.
“This gives us that ever much more documentation to go back next year [to the Congress] and say something needs to be done,” she said, “instead of pretending these kids are learning-disabled or emotionally disturbed, which is total nonsense.”
“There’s no question,” said Alan J. Zametkin, the primary author of the study, “that this is going to be a critical point in the debate over whether the disorder is going to be classified as a handicapping condition.”
For his study, Dr. Zametkin used a brain-imaging technique known as positron-emission tomography, or pet scans, to measure the rates at which the brains of 75 adults used glucose.
He said the researchers chose to work with adults, even though the disorder is more common in children, because the low doses of radiation emitted by the scans could pose a health risk. “We didn’t feel we could ethically justify starting the tests on children,” he said.
One-third of the group studied consisted of adults who had had attention-deficit disorder since childhood and who had never taken stimulants to remedy it. They were also parents of hyperactive children. Studies have indicated that about one-quarter of the parents of such children are hyperactive themselves.
The other 50 members of the group had no history of the disorder.
While the researchers watched the subjects’ brain images, all of the subjects performed a simple test that required them to pay close attention. They were asked to close their eyes, listen for three tones, and push a button every time they heard the softest tone.
When the researchers compared the subjects who had a history of attention deficits with the control group, they found the rate of glucose metabolism was an average of 8 percent lower in those with the disorder.
Moreover, brain activity in the subjects with the disorder was slowest in the areas of the brain known as the premotor cortex and superior prefontal cortex--regions that have previously been shown to control attention and motor activity.
Gabrielle Weiss of Montreal Children’s Hospital, who wrote an editorial accompanying the journal article, said it could be a “landmark paper.”
While researchers have long suspected the disorder has some basis in brain function, experts said, few previous studies have made the link so clearly.
Of particular interest in the debate over special-education services, said James Swanson, director of the Child Development Center at the University of California in Irvine, is that the lower metabolism rates were found in areas of the brain not associated with learning disabilities.
Groups opposing the attempts this year to expand the special-education definition to include hyperactive children said at the time the change was unnecessary because such children were already getting help under other special-education categories, such as learning-disabled.
“This shows that clearly there’s a biological basis for add, and it’s a different biological basis from reading disabilities or learning disabilities,” Dr. Swanson said of the study.
But a lobbyist who helped organize the effort to defeat the expanded definition said the study would probably not alter the debate. “It almost doesn’t matter what the source of the disorder is,” said Edward Kealy, a lobbyist for the National School Boards Association. “The question is, ‘What is the educational impact?”’
But, in the long run, some researchers said, studies such as this one could address another concern raised in the special-education debate by Mr. Kealy and others: the lack of rigorous criteria for diagnosing the disorder.
Currently, children are diagnosed by gauging the frequency of certain behaviors common to the disorder over a long period of time. Critics have claimed that some of the behaviors, such as being unable to sit still or forgetting to bring pencils to school, are common to many children.
As a result of the new findings, Dr. Zametkin said, a definitive biological test for the disorder could be “5 or 10 years away.” But it is unclear whether such a test could be used on children because of the health risk of exposure to radiation.
“It might provide encouragement for some other biological-based measures that are less invasive,” said Dr. Conners of Duke University.
What is needed now, wrote Dr. Weiss in her editorial, is to determine whether the study subjects “represent a distinct group or whether the findings apply to all children” with the disorder.
Dr. Zametkin said his research team has received permission to conduct the tests on children as young as age 12. Results from that group will be completed in 15 to 18 months.
