New Brain Scan May Diagnose ADHD
By EMMA ROSS - Associated Press Writer
LONDON (AP) December 16, 1999 - For the first time, brain scans
have revealed
measurable biochemical differences in people with attention deficit
hyperactivity disorder, a discovery that could reduce the number of
children mistakenly diagnosed and put on drug treatment,
researchers say.
The diagnosis of ADHD, usually made in school-age children, is
commonly based on observed behavior and some experts believe it is
highly subjective _ essentially just an educated judgment.
Some say the condition is being over-diagnosed in the United
States, exposing children unnecessarily to medication, while others
argue it is not treated often enough.
Earlier studies have shown scans can detect structural
differences in ADHD sufferers' brains, as well as abnormalities in
brain activity, and scientists suspect that defects in genes
relating to the brain chemical dopamine probably are involved.
The latest study, conducted at Massachusetts General Hospital in
Boston and published in this week's issue of The Lancet medical
journal, is the first to show a measurable biochemical abnormality
in people with the disorder.
The method ``is the most promising development I've seen in a
long time in terms of our coming up with an actual physical test
that could help us pin down the diagnosis of ADHD,'' said Dr.
Edward Hallowell, a Boston psychiatrist and expert in ADHD who was
not connected with the research.
The Boston scientists have come up with the most direct
indicator to date, measuring the biochemical balance in the brain
by counting the number of dopamine transporters.
Dopamine is associated with movement, thought, motivation and
pleasure. One brain cell signals another by squirting dopamine.
Then the first cell mops up the released chemical with a structure
called a dopamine transporter.
The researchers scanned the brains of six adults diagnosed with
ADHD and 30 healthy people of the same age after injecting both
groups with a chemical agent that attaches to the dopamine
transporter.
The ADHD sufferers had 70 percent more dopamine transporters
than their healthy counterparts.
The scientists could not tell, however, whether that was a cause
or an effect of the disorder.
The increased number could either mean not enough dopamine is
floating around the system or that too much is being produced, said
one of the researchers, Dr. Bertha Madras, a professor of
psychobiology at Harvard Medical School.
``It's very early days, but if all hyperactive adults and
children show a 70 percent increase above normal in this test, I
think it would de facto be considered a diagnostic,'' Madras said.
The researchers used Single Photon Emission Computed Tomography,
or SPECT, scans to study brain activity using radioisotopes.
ADHD has been estimated to affect 3 percent to 5 percent of
school-age children in the United States, and about 1 percent of
children in Europe.
The disorder is characterized by impulsive behavior and
difficulty paying attention and keeping still to read, study or
even watch television. Some mild forms of the symptoms are common
in many children, leading to the concerns that it is diagnosed too
often.
Dr. Sam Tucker, a London-based pediatrician who specializes in
ADHD, said that while the test could be useful, its potential as a
definitive diagnostic test is uncertain.
``Scanning is the way to go, but this alone is not going to be
the whole answer,'' he said. ``I wouldn't use this as a diagnostic
because the neurochemistry is extremely complicated and we don't
know how many chemicals are important. It may be two, it may be
several.''
The researchers agreed doctors still will have to evaluate a
child's behavior to help them diagnose the disease, but said the
new test could be an important tool.
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Judith Richards, London, Ontario, Canada
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