Placebo Effect Probed in Parkinson's
By Adam Marcus - HealthScout News Reporter
THURSDAY, Aug. 9, 2001 (HealthScoutNews) -- Scientists have long
believed that Parkinson's disease patients seem to be
highly susceptible to the placebo effect. Now they know more about why.
Sham treatment of people with Parkinson's triggers a flood of the same
brain messenger molecule that "active" drugs
target -- and from the same region of the brain that's damaged by the
disorder, new research says.
"We conclude that dopamine release in the nigrostriatal system is linked
to expectation of a reward -- in this case the
anticipation of therapeutic benefit," write the authors, led by Raul de
la Fuente-Fernandez, a visiting scientist at the
University of British Columbia's Neurodegenerative Disorders Center.
The findings, which appear in the Aug. 10 issue of Science, also might
explain how the placebo effect works in patients
with other conditions since dopamine is intimately involved in the
brain's reward mechanism.
"To our knowledge this is the first time that anyone has demonstrated a
chemical or physiological basis for the placebo
effect," says co-author Dr. Jon Stoessl, a neurologist at the University
of British Columbia.
The legitimacy of the placebo effect was challenged earlier this year by
Danish researchers who reported in the New
England Journal of Medicine that the phenomenon is largely overstated.
If it exists at all, they said its impact is minor
and almost entirely limited to easing pain.
"Clearly, we disagree with their conclusions," says Stoessl, whose group
is preparing a rebuttal to that study.
Stoessl and his colleagues studied the impact of a saltwater solution on
the brains of six Parkinson's patients who also
received the drug apomorphine, which stimulates dopamine receptors.
Using positron emission tomography (PET)
scanning, the researchers saw that the addition of the placebo sparked
as much as a 19 percent increase in dopamine
activity in the brain.
"The magnitude of the effect is quite substantial and much larger than
most people would have anticipated," Stoessl
says.
But other researchers reacted warily to the latest work.
"There is no question that the psychological setting of a person can
temporarily influence" a Parkinson's patient's
symptoms, says Dr. Abraham Lieberman, a neurologist at the University of
Miami and medical director of the National
Parkinson Foundation.
Lieberman says patients confined to wheelchairs have been known to jump
to their feet in a fire, while tremors and
other motor symptoms of the disease often change during periods of
stress, a phenomenon called "kinesia paradoxica."
Yet once the danger or stress has passed, the immobility returns. "The
trouble is, we can't control it," he says.
Dr. Raj Pahwa, who directs the Parkinson's Disease Clinical and Research
Center at the University of Kansas in
Kansas City, says he has "a lot of concerns" about the latest study.
"They did in it just six patients, and they studied a very short-acting
drug," says Pahwa. "The issue is for how long [the
placebo effect lasts]. It's not whether they get a benefit or not. We
have known forever that patients with Parkinson's
definitely have placebo responses."
What's more, Pahwa says apomorphine comes as an injection, not a pill,
which might increase its effect on patient
psyche more than tablets.
However, Stoessl says the injection was "minuscule" and probably
insufficient to signal a surge of dopamine.
Copyright © 2001 Yahoo! Inc.
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Judith Richards, London, Ontario, Canada
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