Pain threshold can be raised by altering brain chemistry

46 per cent of people in Britain estimated to suffer from chronic pain. Picture: PA

Scientists have shown for the first time that the numbers of opiate receptors in the brain increases to combat severe pain in arthritis sufferers.

Chronic pain – defined as pain which lasts for more than six months – is a real problem for many people with 46 per cent of people in Britain estimated to suffer from it, and making up one in five GP consultations.

But some people seem to cope better than others with pain.

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 researchers have 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, Dr Christopher Brown and his colleagues at Manchester University showed that the more opiate receptors there are in the brain, the higher the ability to withstand the pain.

Researchers used positron emission tomography imaging on 17 patients with arthritis and nine healthy controls to show the spread of the opioid receptors. This suggests the increase in opiate receptors in the brain is an adaptive response to chronic pain, allowing people to deal with it more easily.

Dr Brown said: “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. 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.”

Professor Anthony Jones, director of the Manchester Pain Consortium, which is focused on improving the understanding and treatment of chronic pain, said: “This is very exciting because it changes the way we think about chronic pain.

“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 up-regulate their resilience to pain.

“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.”