<p>Researchers link hyperactivity to an abnormality in the brain
</p>
<p> 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.
</p>
<p> 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."
</p>
<p> 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.
</p>
<p> 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.
</p>
<p> 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.
</p>
<p>By Philip Elmer-DeWitt. Reported by Andrew Purvis/New York.
