Placebo Sparks Brain Painkillers
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PLACEBO SPARKS BRAIN PAINKILLERS
August 24, 2005
US researchers say they have evidence of why some people get pain relief
from sham treatment.
They looked at the so-called placebo effect -- when a person is successfully
treated by a dummy drug just because they believe it works.
Using brain scans the University of Michigan Health System scientists found
placebo treatment triggers the brains natural painkillers, called
Their work on 14 volunteers appears in the Journal of Neuroscience.
Researchers have already shown that some people given a placebo experience
reduced pain sensation and have lower activity in brain regions that process
pain as a result.
Dr Jon-Kar Zubieta and his team set out to see precisely what was happening
in the brain.
They injected a salt water solution into the jaw muscles of the volunteers
to cause pain.
At the same time, the volunteers had their brains scanned by a positron
emission tomography (PET) scanner that would show up any endorphin activity.
During one of the scans, the volunteers were told they would also receive a
medicine that might relieve the pain. This medicine was actually a dummy
Throughout the experiments the volunteers were asked to score their level of
pain and what they were experiencing.
After they received the placebo, nine of the volunteers reported much less
pain and were able to tolerate higher doses of the pain-inducing salt water
Their brain scans also showed that they had more endorphin activity after
simply being told they were about to get the "medicine".
The most pronounced effects were seen in four parts of the brain known to be
involved in processing and responding to pain, namely the left dorsolateral
prefrontal cortex, the pregenual rostral right anterior cingulate, the right
anterior insular cortex and the left nucleus accumbens.
Furthermore, activity in the dorsolateral prefrontal cortex was associated
with the expectation of pain relief.
Activation of the other brain areas was associated with relief of the
intensity of pain, how unpleasant it was and how the individuals felt
emotionally during the pain.
Dr Zubieta said the findings show that the placebo effect is not purely
psychological and has, at least partly, a physical explanation.
"The endorphin system was activated in pain-related areas of the brain, and
that activity increased when someone was told they were receiving a medicine
to ease their pain."
Dr George Lewith from Southampton University, who has studied the placebo
effect and acupuncture, said: "I'm not at all surprised by the findings.
"They are consistent with what we know and have suspected. There is a
physical side to the placebo response. You get a physiological change
induced by expectancy."
He said that research so far suggested that 80-90% of people who benefit
from analgesic drugs would probably get relief from a placebo too.
RELATED NHNE NEWS LIST ARTICLES:
ACUPUNCTURE, REAL OR FAKE, MAY HELP MIGRAINES (5/3/2005):
FIRST GLIMPSE OF MECHANISTIC EXPLANATION FOR PLACEBO EFFECT (5/19/2004):
COUGH MEDICINES 'NO MORE EFFECTIVE THAN PLACEBOS' (6/24/2002):
PLACEBOS FIGHT DEPRESSION AS WELL AS DRUGS (5/8/2002):
THE NOCEBO EFFECT: PLACEBO'S EVIL TWIN (5/2/2002):
THE PLACEBO EFFECT: THE POWER OF NOTHING (5/26/2001):
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Published by David Sunfellow
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