The study, which could lead to better pain management, appears in the latest Proceedings of the National Academy of Sciences.
"We have all met people who seem very sensitive to pain as well as those who appear to tolerate pain very well," says lead researcher Robert C. Coghill, PhD, a professor of neurobiology and anatomy at Wake Forest University Baptist Medical Center, in a news release.
Patients are asked to rate their pain -- on a one to 10 scale -- so doctors can prescribe medications for pain management. "Until now, there was no objective evidence that could confirm that these individual differences in pain sensitivity are, in fact, real," he says.
The most difficult aspect of treating pain has been having confidence in patients' reports of pain, says Coghill. These findings confirm that the level of pain intensity can be seen in brain activity.
The study itself included 17 healthy men and women who agreed to have a computer-controlled heat stimulator placed on a leg. While researchers watched each patient's brain activity -- via what's known as functional magnetic resonance imaging (fMRI) -- the device heated a small patch of their skin to a temperature most people find painful.
The volunteers reported very different experiences of pain, reports Coghill. The least-sensitive person rated the pain around "one" while the most-sensitive person rated it as a "nine."
Their brains reflected the differences, he explains. Those who gave a higher pain number had greater activation in the "pain" brain area; those with the least sensitivity had less brain activity.
The pain "experience" is likely due to a combination of factors, like the person's past experience with pain, his or her emotional state when experiencing the pain, and the person's expectations regarding pain, he adds.
In prescribing medications for pain management, doctors can trust what their patients are saying about the intensity of their pain, he says.