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How your brain processes pain (2/25/11)

February 25, 2011

Does What You Expect Change  What You Get?

Pain is information, how the brain interprets certain stimuli to form sensations almost all humans fear and detest.   As Oxford researchers reported last week in Science Translation Medicine, how we individually interpret pain is markedly changed by context:

The Study

Subjects – 22 healthy people

Method – Heating their legs and asking them how much pain they experienced

Intervention – intravenous drip of remifentanil, a fast acting pain killer not available in the US but similar in effect to fentanyl

What Happened

Heating up the legs alone – average score of 66 on range of 0-100, with 100 equaling terrible pain

Score reduced to 55 when remifentanil was injected without their knowledge

Score reduced to 39 when they were told that got the drug

Last –

When told the painkiller was withdrawn and that their pain level might jump, the scores rose back to average 64 – and they were still on the painkiller.

The Power of Expectation

Psychologists talk of the “cognitive set,” the expectations and context of what happens to people.

Cognitive set change behavior.  Tell people that the oregano they’re smoking is marijuana, and some will report getting high.  Others, given the same meal in a blue red rather than a red painted room, will eat on average one-third less.

How the brain processes information changes how we interpret it – and what we do.

In this study, people given a painkiller, without knowing it was infused, felt less pain.  Told they were on a painkiller, their pain went down far, far more.

Yet told the painkiller was no longer being infused, their pain quickly went up and up  – just as high as when it was without the painkiller – even though the same amount was coursing through their arteries.

In acute pain, expectations matter greatly.


Professor Irene Tracey, who helped with the study, was surprised that brain expectations would change pain results so dramatically. If brain expectations could an expand or  inhibit the drug effect so powerfully, such a cognitive set would need to be used in all further acute pain studies.

We can hope so.  Getting researchers to fully study the complicated turns of the placebo effect is both difficult and time consuming.  That it should be done does not mean that it will.

More interesting results may come from using these types of effects with clinical populations.  It’s been known for quite a while how much patient expectations modify subjective pain relief.

Many know that acupuncture can work so effectively that major surgery can be done after applying only a few needles.  However, cognitive expectations directly impact the results.  Acupuncture works far more effectively in China than the US.  Therapies work better when people’s cultural expectation is that they will work.

However, for Western populations, other techniques varying from relaxation to meditation to guided imagery should help patients with acute pain.

Chronic Pain

Many techniques need to be tried to mitigate the acute painful effects of medical procedures and diagnostic regimens.  Acute pain is however, a different animal from chronic pain.

Chronic pain patients have experienced their symptoms generally for years or decades.  Such prolonged neurologic stimulation changes the brain.  It certainly changes how patients respond to common painkillers, like opiates.  Many chronic pain patients report normal painkillers hardly affect them at all.

Yet such a large, suffering population needs all the help they can get.   Even when abnormal brain pathways have long been potentiated, new more normal ones can still be built.

It’s clear cognitive approaches change acute pain.  Different cognitive approaches now need to be combined with other alternative treatments to affect the best results possible.  Now that the government is cracking down on prescription pain drug use, the need for different ideas is greater.

And much can be improved.  Because in the end it’s always the brain that modifies the feeling of pain.Rest, sleep, Sarasota Sleep Doctor, well-being, regeneration, longevity, body clocks, insomnia, sleep disorders, the rest doctor, matthew edlund, the power of rest, the body clock, psychology today, huffington post, redbook, longboat key news

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