When the body is faced with chronic pain, the brain responds by increasing the number of opiate receptors at its disposal. Such were the findings from researchers at the University of Manchester who used PET imaging on patients suffering from severe arthritis.

The researchers were compelled by the question: what makes one person cope better with pain than another person? An increase in opiate receptors would diminish the intensity of pain, and for patients experiencing an enduring type of pain, that increase might explain why they sometimes tolerate the pain more successfully.

Looking at animal models of chronic pain, the researchers already had some reason to speculate on these findings but, until now, they said there has not been scientific evidence to confirm it.

“As far as we are aware, this is the first time that these changes have been associated with increased resilience to pain and shown to be adaptive," said Dr. Christopher Brown, one of the researchers. “Although the mechanisms of these adaptive changes are unknown, if we can understand how we can enhance them, we may find ways of naturally increasing resilience to pain without the side effects associated with many pain killing drugs.”

“There is generally a rather negative and fatalistic view of chronic pain. This study shows that although the group as a whole are more physiologically vulnerable, the whole pain system is very flexible and that individuals can adaptively upregulate their resilience to pain," said professor Anthony Jones, director of the Manchester Pain Consortium, a group dedicated to improving the way pain is understood and treated.

“It may be that some simple interventions can further enhance this natural process, and designing smart molecules or simple non-drug interventions to do a similar thing is potentially attractive," he continued.

The research was published in the journal Pain, with research funding from the Medical Research Council.