Why Junior Won't Sit Still

By Philip Elmer-DeWitt

For a disorder that is as widespread and as closely studied as hyperactivity, scientists know precious little about it. Lots of children -- and many adults, for that matter -- have trouble paying attention and keeping still. But without a clear understanding of what causes the syndrome now known as attention deficit-hyperactivity disorder, parents and teachers have no surefire way of distinguishing true hyperactivity from other learning disabilities, an abused-child situation or just plain bratty behavior. Doctors have long suspected there was a real physiological problem lurking behind the psychosocial maladjustment, but in more than 20 years of intense scientific scrutiny, no one was able to find the key.

Until now. In a landmark study that could help put to rest decades of confusion and controversy, researchers at the National Institute of Mental Health have traced ADHD for the first time to a specific metabolic abnormality in the brain. The findings, published in the current issue of the New England Journal of Medicine, could lead to a much needed diagnostic test and should silence skeptics who maintained that the disorder resided more in the minds of grownup specialists than in the unruly children they were trying to control. Says Dr. Alan Zametkin, a psychiatrist at the NIMH who directed the study: "We would hope that people would stop blaming parents and bad parenting and intolerant schools for this problem."

In the NIMH study, researchers used a new and sophisticated brain-imaging technique known as positron emission tomography scanning to measure metabolic activity in the brain cells of 25 adults who had been hyperactive since childhood and had at least one child with the same problem. The results were striking. Not only was overall brain metabolism 8% lower in hyperactive subjects than in a control group, but also the largest differences were found in two regions of the brain -- the premotor cortex and the superior prefrontal cortex -- known to be involved in regulating attention and motor control. It is still not clear what causes these metabolic differences (although heredity is known to play a role), but the link between brain chemistry and behavior now seems certain.

Hyperactivity is thought to affect as many as 4% of school-age children, appearing eight times as frequently in boys as in girls. In all, there could be as many as 2 million hyperactive youngsters in the U.S. alone. But until a definitive test is devised, no one can be sure. Most children suspected of being hyperactive are treated with low doses of amphetamine-like stimulants, usually Ritalin, which paradoxically seem to calm the youngsters down. Ritalin, combined with counseling and special education, can be an effective treatment for truly hyperactive children. But there can be side effects, including insomnia, listlessness and temporarily stunted growth, and critics contend that the drug is widely overprescribed. In Baltimore County, Md., which seems to rely on such medication more heavily than places elsewhere, nearly 6% of all school-age children were regularly dosed with stimulants as recently as 1988.

Last week's report promises to change all that. It could spur the development of an effective test that would distinguish between those children who need drugs or other therapies and those who do not. More important, a better understanding of the physical roots of hyperactivity could lead to improved treatments that might relieve children of their metabolic problem -- without giving large numbers of them powerful drugs.

With reporting by Andrew Purvis/New York