Expectations about pain can affect its intensity, research shows

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Expectations about pain can affect its intensity, research shows

http://www.medicalnewstoday.com/medicalnews.php?newsid=30233

06 Sep 2005

When it comes to controlling pain, positive thinking can be as

powerful as a shot of morphine, according to new brain imaging

research at Wake Forest University Baptist Medical Center. Lowering

participants' expectations about pain levels reduced both pain-

related brain activity and how much pain they felt.

The study is reported on-line this week in the Proceedings of the

National Academy of Sciences.

" We found that expectations have a surprisingly big effect on pain.

Positive expectations produced about a 28 percent decrease in pain

ratings - equal to a shot of morphine, " said Tetsuo Koyama, M.D.,

Ph.D, a post-doctoral fellow and lead author of the study.

The study involved 10 normal, healthy volunteers who had a heat

stimulator applied to their legs while their brains were being

scanned with functional magnetic resonance imaging (fMRI), a

technology that shows which areas of the brain are being activated.

In a training session, researchers taught participants to expect

three different levels of painful heat stimuli after a timed

interval. A seven-second interval signaled a heat level that caused

mild pain (115 degrees Fahrenheit), a 15-second interval signaled a

heat level that produced moderate pain (118 degrees) and a 30-second

interval signaled a heat level that produced severe pain (122

degrees). Since the heat stimuli were on for only 20 seconds, none of

them were hot enough to cause burns or damage to the skin.

One or two days after training, participants underwent 30 different

heat trials that were monitored with fMRI. About a third of the time,

the researchers mixed the signals for the pain levels, so that

participants were expecting one temperature, but actually received

either a higher or lower temperature.

When participants expecting moderate pain were exposed to the severe

heat level, their ratings of pain intensity were 28 percent lower

than on the trials where they were expecting a high level of pain and

actually received it. All 10 subjects had diminished pain intensity

when they expected lower levels of pain.

" Expectations of decreased pain powerfully reduced both the

subjective experience of pain and activation of pain-related brain

regions, " said Coghill, Ph.D., the senior author of the study

and a neuroscientist at Wake Forest University School of Medicine,

which is part of the Medical Center.

Brain regions activated during expectations of pain overlapped

partially with those activated during pain, which suggests that there

is are crucial brain regions that allow expectations to shape the

processing of information from the body.

" We don't experience pain in a vacuum, " Coghill said. " Pain is not

solely the result of signals coming from an injured body region, but

instead emerges from the interaction between these signals and

cognitive information unique to every individual. "

He said that the identification of brain regions that can allow

cognitive factors such as expectations to shape incoming sensory

information may lead to increased acceptance of cognitive and

behavioral treatments for pain by patients, physicians and insurers.

" We need to find ways to optimize these treatments, " Coghill

said. " Pain needs to be treated with more than just pills. The brain

can powerfully shape pain, and we need to exploit its power. "

The research was funded by the National Institute of Neurological

Disorders and Stroke.

Coghill's other colleagues on the research were McHaffie, Ph.D.,

a neuroscientist, and J. Laurienti, M.D., Ph.D., a radiologist,

from Wake Forest Baptist. Next, Coghill would like to learn how

optimists and pessimists differ in their perceptions of pain.

Wake Forest University Baptist Medical Center

http://www.wfubmc.edu