New Brain Scan May Diagnose ADHD

[judith richards <judithr@xxxxxxxx>]

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.

~~~~
Judith Richards, London, Ontario, Canada
judithr@xxxxxxxx
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