The complex world of pain

Little is known about how the brain works

The reason people perceive pain in different ways could be down to the complex way in which the brain interprets it, according to scientists.

Until the 1960s, it was thought that pain was a relatively straightforward phenomenon, caused by tissue damage.

But now scientists believe it could be influenced by genetic, environmental and other factors.

Writing in The Lancet, Dr John Loeser of the University of Washington and Professor Ronald Melzack of McGill University in the USA say it is clear the central nervous system modifies pain signals.

This can, for example, be because some people with previous experience of pain and suffering anticipate it.

Impervious to pain

The researchers say the complexity of the brain's response to pain signals may explain why some people with chronic pain respond to psychological treatment such as behavioural and cognitive therapies.

Or why some people who have had a limb amputated continue to complain of suffering when there is no evidence of tissue damage, while others appear not to be affected by it even when there is proof of harm.

They write: "It is possible that, just as the brain is modified by experience, especially in early life, the brain may be capable of altering the way pain-producing information is processed to keep its impact to a minimum."

They also argue that pain may be affected by levels of stress hormones produced to fight tissue damage.

The researchers conclude that research into how the brain works is only in the early stages and that many people still complain that they are given inadequate treatment for pain.

Pain is thought to be the most common reason people consult their doctors.

The NHS budget for treating chronic pain is estimated to be enormous, as is the cost of benefits for people who cannot work because of it.

Drug companies are increasingly looking at the complex interactions in the brain as part of their research into the development of new treatments.

But, according to one French phsyiopharmacology specialist, Dr J. Besson, a major breakthrough could still be a long way off.