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People who fear pain are more likely to suffer it

BY TRACIE WHITE

Each of us responds differently to pain. Exactly what causes this variation is a matter for debate—why one person's forgotten hangnail becomes another's migraine headache. But a study, published in the January issue of the journal Pain, shows that fear and anxiety about pain may account for a good deal of the individual variations in how much pain we feel.

"This study has some pretty strong implications," said Sean Mackey, MD, PhD, assistant professor of anesthesia and co-author of the study. "If we can learn to control the fear about pain, maybe that will help us better control the pain."

The study is the first to show the influence of fear and anxiety on the experience of pain by actually looking at the brain. Using functional magnetic resonance imaging—a technology that traces brain activity and has been used to study pain since the late 1990s—researchers have been able to pinpoint the areas in the brain responsible for fear and anxiety related to physical pain.

"I can tell you as a pain doctor that fear is the No. 1 issue that I deal with in helping people to better manage their chronic pain," said Mackey. "I was interested in doing this study because I have a strong belief that fear and anxiety play a significant role in how we perceive pain and how we all perceive pain differently."

To study these relationships, researchers began by administering various psychological tests to their human subjects to determine individual anxiety levels. The first, the Anxiety Sensitivity Index questionnaire, measured the subjects' levels of anxiety about different physical sensations like heart palpitations or stomachaches. For example, it measured whether they might interpret a bad stomachache to mean they had stomach cancer or had just eaten a bad pizza for lunch. The second, the Fear of Pain Questionnaire, measured fear levels for different types of physical pain ranging from a paper cut to a broken neck.

Participants were then subjected to varying levels of pain applied to their forearms with a heat probe—never hot enough to damage tissue but enough to be uncomfortable. While the pain was administered, researchers collected images of their subjects' brains.

Finally, researchers correlated the questionnaire scores with brain activity in specific regions of the brain.

The study found a high correlation between the Fear of Pain Questionnaire and the right lateral orbital frontal cortex, an area of the brain that when activated may reflect attempts by fearful individuals to evaluate and/or regulate responses to pain.

There was also a high correlation between the Anxiety Sensitivity Index and the medial prefrontal gyrus—the region of the brain involved with self-focused attention about, or reflection on, one's own body. In other words, it's the area that searches for things that are wrong.

The correlations were "insanely strong," said co-author Kevin Ochsner, a former Stanford researcher now an assistant psychology professor at Columbia University. "It took us all by surprise."

Researchers concluded that there are significant differences with perception of pain between people and that these individual differences may be accounted for by differing fears and anxieties related to their pain.

"This is only the first step in work that might look at this issue," said Ochsner, who is hopeful further research can lead to a better understanding of anxiety and its relationship to pain.

"We want to know how people use cognitive strategies to make neutral what was once really negative," Ochsner said. "What are the brain systems and psychological processes that help turn off painful experiences?"