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 Underlining the power of expectations, the motor improvements,
measured by a standard Parkinson's assessment, occurred even though
both injections contained only saline and no active ingredients.
The research, said an editorial in the journal Neurology, which
published it, "takes the study of placebo effect to a new
dimension."
More and more studies have documented the power of placebos, in
which patients experience an improvement in symptoms despite
receiving sugar pills, sham surgery, or other intervention with no
intrinsic therapeutic value. Placebo responses have been shown to
alleviate pain, depression, and osteoarthritis, among other
conditions.
That has posed challenges for drugmakers, since clinical trials
typically pit an experimental compound against a placebo. When
placebos are powerful, actual drugs often fail to best them.
Earlier studies have shown that patients' expectations can lead to
improvements in Parkinson's, a progressive motor disease in which
the brain's production of dopamine plummets.
As it happens, dopamine release is increased by belief, novelty, and
the expectation of reward - mental states that underlie placebo
effects, said neurologist Alberto Espay of the University of
Cincinnati, who led the new study.
He and colleagues told 12 Parkinson's patients they would receive
shots of two formulations of equal effectiveness of the same drug,
getting the second after the first wore off. One cost $100 to
manufacture, they were told; the other, $1,500.
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In reality, both were saline.
When patients received the "$1,500" drug first, their motor function
improved two-fold compared to cheap placebo, and 28 percent over
baseline, but less than with the Parkinson's drug levodopa.
Because the study deceived the 12 volunteers, usually a bioethics
no-no, it received extra scrutiny from the review board that okays
human research.
When the volunteers were debriefed, Espay said, eight said they
expected the "expensive" drug to be more effective; they experienced
the greatest improvement relative to the "cheap" injection. Four
said they had no expectation of greater benefits, "and they showed
little overall changes" in motor function, Espay said.
Ordinarily, a study with only a dozen people would not be published
in a top journal. But because earlier studies, going back more than
a decade, have also shown a placebo effect in Parkinson's, the
research has greater credibility, experts said.
(Reporting by Sharon Begley; Editing by Nick Zieminski)
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