However, some people seem to cope better than others with pain, and knowing more about how these coping mechanisms work might help to develop new ways of treating this distressing symptom, researchers said.
It has been known for a long time that we have receptors in our brains that respond to natural painkilling opiates such as endorphins, but the researchers have now shown that these receptors increase in number to help cope with long-term, severe pain.
By applying heat to the skin using a laser stimulator, researchers from the University of Manchester in UK showed that the more opiate receptors there are in the brain, the higher the ability to withstand the pain.
The study used Positron Emission Tomography (PET) imaging on 17 patients with arthritis and nine healthy controls to show the spread of the opioid receptors.
This suggests that the increase in opiate receptors in the brain is an adaptive response to chronic pain, allowing people to deal with it more easily.
"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 Christopher Brown, from The University of Manchester.
"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," he said.
"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 Anthony Jones, director of the Manchester Pain Consortium in UK.
"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," said Jones.
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