PLACEBOS MIGHT HOLD PROMISE IN DRUG TREATMENT

There's no denying the power of the mind over the body. Ask any drug addict.

As St. Augustine said in his Confessions, "The mind commands the body, and
it obeys."

But you could find a few scientists who would deny one prominent medical
example of mind over matter - the effectiveness of placebos, "medicines"
with no active ingredients.

When a study published last year questioned the reality of the placebo
effect, most doctors shrugged. They knew that placebos often work. If a
study suggested otherwise, there must be something wrong with the study. On
the other hand, nobody can say with any certainty how placebos work their
magic. So the effectiveness of placebos is not exactly supported by a firm
scientific foundation.

Of course, without understanding how placebos are supposed to work, it
would be difficult to know whether studies to test them are properly
conducted. In fact, that may be why last year's study failed to find
substantial evidence in favor of placebo effectiveness, write Raul de la
Fúente-Fernández and A. Jon Stoessl of the Pacific Parkinson's Research
Centre at the University of British Columbia.

Last year's study, reported in The New England Journal of Medicine , was
actually a study of studies, an analysis of numerous published reports on
placebo effects.

"The studies included in this analysis might not have been optimal to
address the issue," Drs. Fúente-Fernández and Stoessl write in the June
issue of Trends in Neurosciences.

Placebos are most commonly used to relieve pain. But they can have many
other more specific effects, especially in Parkinson's, a disorder marked
by tremors and problems with muscle control. Several studies have shown
substantial improvements in various Parkinson's symptoms for patients given
a placebo in clinical trials of real drugs.

Studying the placebo effect in Parkinson's, Drs. Fúente-Fernández and
Stoessl suggest, may help scientists understand placebos in general.
Studies so far, these researchers say, indicate that placebos might work
much like addictive drugs.

Addictive drugs hijack the brain's reward system, promising pleasure even
when the addict knows that the ultimate result will be pain. Most addictive
drugs stimulate certain brain cells to release dopamine, sometimes known as
the "pleasure" molecule.

Placebos also offer a promise of some benefit, and Drs. Fúente-Fernández
and Stoessl think they may also work by stimulating dopamine production.

Addicts, one school of thought holds, have deficient dopamine systems.
Drugs are "unnatural" rewards that temporarily close the dopamine gap in
certain parts of an addict's brain.

Some studies have shown, though, that it's not exactly the reward from the
drug itself that matters, but the expectation of a reward. Perhaps, Drs.
Fúente- Fernández and Stoessl say, placebos work the same way.

After all, there is no particular reason to expect a sugar pill or
injection of salt water to elicit any significant specific bodily response.
But expectations do cause physiological reactions. Remember, Pavlov trained
his dogs to salivate at the sound of a bell that triggered an expectation
of eating.

And it's clear that expectation plays a big role in a placebo's effects.
Placebos can make blood pressure or heart rate go either down or up,
depending on whether the patient thinks the placebo is a tranquilizer or a
stimulant.

Recent studies support this idea. A brain scan study of Parkinson's
patients showed increased dopamine release in response to injection of a
salt solution. All patients showed more dopamine release, but not all
experienced a placebo benefit. It seems, then, that the dopamine release
was triggered by the expectation of a benefit, not a benefit itself.

Since dopamine has long been known to be a critical molecule in Parkinson's
disease, its role in a Parkinson's placebo effect is not surprising. But
Drs. Fúente-Fernández and Stoessl surmise that dopamine may be important in
other instances of placebo effectiveness.

One study has shown that placebos for pain affect the same parts of the
brain as pain-killing opiate drugs, which interact with dopamine.

Depression, another disorder sometimes helped by placebos, might also be
affected by dopamine levels.

In any event, if placebos work by affecting dopamine - and by mechanisms
similar to the workings of addictive drugs - the obvious implication is
that understanding placebos might offer insight into addiction. Placebos,
in fact, might become useful long-term treatments for addiction in the form
of "substitute drugs."

Actually, there were signs in a study from nearly half a century ago that
salt water injections could help treat morphine addiction. More recent
studies suggest similar placebo benefits for heroin users.

Naturally, there's a downside - researchers have long known that placebos
sometimes seem to become addictive themselves, with patients showing
withdrawal signs after their placebo doses had been discontinued.
Nevertheless, addiction to some things is not as bad as addiction to others.

"Although there is the potential for placebo addiction," write Drs.
Fúente-Fernández and Stoessl, "a reduction in the use of illicit drugs
would represent a major achievement in terms of health and social safety."

-- MAP Posted-by: La