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Placebo sparks brain painkillers

US researchers say they have evidence of why some people get pain relief from sham

treatment.

They looked at the so-c alled placebo effect - when a person is suc ces sfully treated by a dummy

drug just bec ause they believe it works.

Using brain sc ans the University of M ichigan Hea lth System sc ientists found placebo treatment

triggers the brains natural painkillers , called endorphins.

Their work on 14 volunteers appears in the Journal of Neuroscienc e.

Physical phenomenon

Researchers have already s hown that some people given a plac ebo experience reduced pain

sens ation and have lower ac tivity in brain regions that proces s pain as a result.

Dr Jon-Kar Zubieta and his team set out to s ee precis ely what was happening in the brain.

The endorphin system was activated in pain-related areas of t he brain

Researcher Dr Jon-Kar Zubieta

They injec ted a sa lt water solution into the jaw musc les of the volunteers to caus e pain.

A t the same time, the volunteers had their brains s canned by a positron emiss ion tomography

(PE T) sc anner that would show up any endorphin activity.

During one of the s cans , the volunteers were told they would also receive a medicine that mightrelieve the pain. This medicine was ac tually a dummy drug.

Throughout the experiments the volunteers were asked to sc ore their level of pain and what they

were experienc ing.

A fter they rece ived the plac ebo, nine of the volunteers reported much les s pain and were able to

tolerate higher doses of the pain-inducing s alt water injec tions.

"Natural" painkillers

Their brain s cans als o s howed that they had more endorphin activity a fter s imply being told they

were about to get the "medic ine".

The most pronounced effec ts were seen in four parts of the brain known to be involved inproces s ing 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 acc umbens.

There is a physical side to the placebo response

Dr George Lewith from Southampton Univers ity

Furthermore, activ ity in the dorsolateral prefrontal c ortex was ass ociated with the expec tation

of pain relief.

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A ctivation of the other brain areas was ass ociated with relief of the intensity of pain, how

unpleasant it was and how the individuals felt emotionally during the pain.

Dr Zubieta s aid the findings s how that the placebo effect is not purely psychological and has, at

least partly, a phys ical explanation.

"T he endorphin sys tem 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 Univers ity, who has s tudied the placebo effect and

acupuncture, said: "I'm not at all s urprised by the findings.

"T hey are consis tent with what we know and have suspected. There is a physic al s ide to the

placebo response. You get a physiological c hange 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.

Story from BBC NEWS:

http://news.bbc.co.uk/go/pr/fr/-/2/hi/health/4176078.stm

Published: 2005/08/24 09:22:58 GMT

BBC 2011