Pain? Don't give it another thought

Or so says Professor Patrick Wall, who argues that we can think even the most intense pain away by refusing to pay attention to it

An army major was skiing with his squad in Switzerland when the ground literally gave way beneath his feet. He slid down the wall of the crevasse that had formed and fell into a crack in the ice. He was so firmly wedged he could not move his legs and one of his arms was jammed above his head. It was later discovered that the soldier had dislocated his shoulder, broken his collar bone and severely bruised his legs and pelvic region. Yet it was not until an hour after his fall that he felt any pain; in fact, he was so lucid that he was able to supervise his own rescue. The army major had unwittingly and mysteriously broken through the pain barrier.

An army major was skiing with his squad in Switzerland when the ground literally gave way beneath his feet. He slid down the wall of the crevasse that had formed and fell into a crack in the ice. He was so firmly wedged he could not move his legs and one of his arms was jammed above his head. It was later discovered that the soldier had dislocated his shoulder, broken his collar bone and severely bruised his legs and pelvic region. Yet it was not until an hour after his fall that he felt any pain; in fact, he was so lucid that he was able to supervise his own rescue. The army major had unwittingly and mysteriously broken through the pain barrier.

Pain is one of the most misunderstood phenomena of our time. Some people seem to feel pain more than others, we cannot understand another person's pain, and we all fear being in pain. Professor Patrick Wall, from the Centre for Neurosciences in London, has a theory about pain: a "science of suffering" as he calls it. He believes that the word pain hides a multitude of different processes occurring in the body and brain which become subsumed under one overall response.

How we each respond to pain depends on us as individuals, even our culture and the context within which the pain occurred. Wall believes that pain is not just a deeply unpleasant sensation, but an action plan. "What happens when we feel pain is that the brain analyses what has happened, whether it's good or bad, and if we can do anything about it," says Wall.

The old idea about pain is that it exists as a pure, naked sensation; it is then dressed up in our feelings about the pain - how miserable we are, how stupid we were to have hammered our thumb instead of the nail. "I put it all together," says Wall. "This is pain that is a miserable event." His theory is proving controversial. "I'm in a fight against the entire establishment who are soaked in the idea of Cartesian dualism. It's an old battle."

Dualism, the theory that the body and the mind are separate, is not one that Wall has much time for. "If I tell someone I am concerned with the problem of pain, they frequently ask me whether I mean physical pain or mental pain," he says, "but pure pain is never detected as an isolated sensation. Pain is always accompanied by emotion and meaning so that each pain is unique to the individual."

There are all kinds of painful injuries, but what usually happens when a person is hurt is that damaged tissue releases chemicals called peptides which stimulate sensory nerve cells and produce a sensation of pain. As the damaged cells become inflamed, more pain-inducing chemicals are leaked into the body. This excess of chemicals causes the sensory nerves to become more sensitised to pain.

They transmit the message that tissue is damaged by way of the spinal cord, which communicates with various parts of the brain. The brain sends signals back to the spinal cord which decrease or increase the nervous system's sensitivity to the injury. The result is an increase or a decrease in the level of pain. Thus the brain can alter the pain level depending on how much attention is paid to the sensation.

For example, when you give blood, if you watch the needle piercing your skin and blood being sucked into the syringe, you may feel a range of sensations, from deep pain in your arm to an overwhelming nausea. However, thinking about your next holiday, or watching the nurse instead of the needle, can actually decrease the pain. The brain has sent messages to the spinal cord saying there are more interesting matters to pay attention to.

Images from brain scans show how much the role of attention plays in the sensation of pain. Dr Catherine Bushnell, of McGill University in Montreal, Canada, took brain scans of her patients when they were in pain and discovered that four separate regions in the brain responded. Two of the regions in the outer layer of the brain, the cortex, are responsible for feeling touch as well as pain, but the other two regulate emotion and attention. One of the latter regions, the anterior cingulate cortex, is associated with paying attention. It is important for determining how much a pain bothers us, according to Bushnell.

She asked volunteers to put their hands in painfully hot water, and then used hypnotic techniques to persuade them that the water wasn't unpleasant. Not only did the volunteer's subjective impression of the pain lessen, but activity in the anterior cingulate cortex was reduced. "Our psychological state can alter how much pain we feel," says Bushnell.

Other main areas in the brain that are involved in the sensation of pain are the motor cortex, cerebellum and basal ganglia - these regions control movement. What happens, says Wall, is that the brain is running through various plans for how to cope with this new sensation - which could involve physical movement.

"I'm not saying you do move, but in terms of thinking what to do, you're using the part of the brain that deals with movement." Wall was the first person to take this into account when he electronically stimulated the motor cortex of a patient to alleviate his pain. This was back in 1967. Now surgeons can implant electronic devices into the motor cortex to stimulate the brains of patients with severe pain. Usually this technique is for people with phantom limbs - the sensation that arises when an amputated limb feels as if it is still present, often very unpleasant as the limb feels twisted in an awkward position.

Wall has had cancer for some years and while treatment is keeping the cancer under control, he does suffer from time to time. When asked if his own research helped him deal with the pain, he said: "Absolutely. It's a matter of attention - I distract myself, I know I'm only in pain when I allow my pain to conquer my attention."

So strong is the power of the mind that treatment which has no scientific credibility can alleviate pain. Ultrasound has often been used to treat inflammation - the idea being that the deep heat produced by absorbing the sound should help reduce swelling. No trials have shown that this is the case, yet ultrasound - or the patient's notion of it being effective - can work.

In a recent study at the Eastman Dental Hospital in London, doctors used ultrasound on patients who had had a tooth extracted. The patients had their face massaged using the machine, but what half the patients did not realise was that the machine was not even switched on. Yet as long as it was the doctor operating the machine, the pain was reduced, as was the swelling in all the patients. "Evidently this placebo response required a doctor in a white coat with an impressive machine," says Wall. He adds that not only did the patients' subjective feelings change, but there was an objective response - the decrease in swelling. "The rational explanation is that the brain affects hormones, which in turn affect inflammation."

Whatever the precise mechanism, the study demonstrates the power of the mind to control or override the brain's pain register - and that there may be some truth behind the notion of mind over matter.

'Pain: The science of suffering', by Patrick Wall, Weidenfeld and Nicholson (£14.99)