If doctors could offer us a world free of pain, would we really want it? Perhaps not, says Geoff Watts.

"For all the happiness mankind can gain/ Is not in pleasure but in rest from pain", wrote poet John Dryden. So he would surely be overjoyed that the past 300 years have delivered the more privileged among us to a freedom from pain unimaginable in the 17th century.

Medical science may not quite have abolished the experience of pain, but it seldom questions the rightness of this as a goal. Contrast that with the attitude of our forebears, many of whom might have been less inclined to ask how we could abolish pain than whether we should.

Throughout most of human history, pain has been regarded as divine retribution or as part of the natural order of things. Enduring it has been held to confer virtue. In a time when pain control was limited or non-existent, such attitudes were understandable: they made the best of an experience that was not only unpleasant but also inescapable. With the advent of effective pain control, these views might have been expected to disappear. Certainly they have faded, but they have not entirely gone. The late Patrick Wall, Britain's most celebrated pain researcher, quotes Pope John Paul II: "What we express with the word suffering seems to be particularly essential to the nature of Man. Sharing in the sufferings of Christ is, at the same time, suffering for the Kingdom of God. Suffering contains, as it were, an appeal to Man's moral greatness and spiritual maturity."

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Wall points out that the pope seems not only to accept suffering but to glorify it. He adds: "This powerful statement has had practical consequences in Catholic countries, particularly in treating terminal cancer, where some doctors have hesitated in their treatment of pain and suffering because the treatment might intrude on the patients' acts of redemption."

Not that you have to go to Catholic countries to find physicians who have pondered the probity of pain relief. In the 1830s James Simpson's introduction of chloroform as an anaesthetic during labour prompted suspicion and even hostility. Fears about its safety may have been justifiable, but many argued that pain during labour was somehow part of the natural order, and not to be ameliorated. Churchmen waded into the argument by quoting Genesis: "In sorrow thou shalt bring forth children."

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The debate was not settled for another 20 years, and then it was by royal rather than medical prerogative. Queen Victoria accepted chloroform during the birth of Prince Leopold - and that was that.

The notion that limiting pain is unnatural comes unstuck when you appreciate that nature itself has evolved pain-limiting mechanisms. Time and again men injured in battle report being unaware that they had been seriously wounded until the conflict had abated. Only then did the pain begin.

The survival value of such arrangements is clear enough. Pain is a message designed to alert the organism that something is wrong. But for a caveman running from a tiger that has bitten off part of his arm, a pain signal would be irrelevant. Indeed it would be counterproductive; excessive awareness of the injury would hamper his efforts to stand and fight, or turn and flee.

The pain-modulating system is sophisticated and not yet fully understood, but the body is known to manufacture molecules called endorphins, which are natural counterparts of the analgesic (anti-pain) drug morphine. Their discovery offers one explanation for soldiers' toleration of battlefield wounds: they are producing their own painkillers. It also explains why drugs such as morphine are such effective analgesics: they work because they are making use of the body's own pain suppression mechanism.

That is not all. In trying to account for the variability of an individual's pain responses from one occasion to another, Wall and his McGill University collaborator Ronald Melzack devised what they called the "gate theory of pain". While some nerves convey pain signals to the brain, others carry messages back from it. The latter can interfere with incoming signals and reduce or block them - close the gate, to use Melzack and Wall's terminology. Conversely, by opening the gate wider, awareness of pain can be heightened. It was the exploitation of this idea that led to the method of pain control known as transcutaneous nerve stimulation. A small electrical stimulus, applied to the correct area of the skin, can be used to close the gate artificially.

Although pain relief is one of the routine functions of the modern doctor, it played relatively little part in medicine before the Renaissance. Not that there was much physicians could have offered apart from mandrake, henbane and alcohol. The advent of opium represented a big step towards more effective analgesia. But it was the 19th century that witnessed the development of our most familiar drugs, including morphine, codeine and aspirin. With the invention of nitrous oxide, chloroform and ether, surgeons no longer needed to equate skill with speed, and patients were spared the ordeal of remaining conscious during risky operations.

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One of the hurdles to good pain control is its subjectivity. Doctors can measure blood pressure or cholesterol and medicate accordingly. But when it comes to pain they can only ask the patient. My "agonising" may be your "slight", and the tendency of medical staff has been to underestimate the severity of pain. One remedy, particularly for dealing with postoperative pain, has been found in patient-controlled analgesia.

A patient using this technique has a motorised syringe that delivers a small dose of pain-killing drug into a vein at the press of a button. Those who want more pain relief press the button more often. Experience shows that among a large group of patients using this method, total drug consumption remains about the same as with conventional prescribing. What does alter is the distribution. Some patients take more, some less.

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Treatment of pain has also been plagued by the assumption that it must have a physical origin. Professionals and lay people have clung to this mistaken view.

Most pain does have a physical origin, whether in the form of a burn, a microbial infection or some other injury, but not always. Chronic afflictions with no apparent cause may begin with an acute response to physical injury that is inappropriately maintained. The injury and all observable signs of damage heal but the pain state set up in the central nervous system lingers.

Andrew Hodgkiss, a psychiatrist at St Thomas's Hospital in London, argues that the medical profession must bear part of the blame for the view that pain must have a physical cause. For him, "pain is a complex lived experience of human beings with roots in their autobiography, their emotional state and their concentration, as well as their sensory input. If we hadn't discarded all those ideas, and gone instead for a simple relationship between disease and pain, we wouldn't be having to struggle with saying it's in the mind. Of course pain is in the mind. It's a lived experience, it's a perception, it's an emotion, it's all these things. All pain is in the mind even if there's a great big lesion."

The futility of continuing to search exclusively for a physical cause when none can be found has major implications for treatment. It has led to the creation of a handful of last-resort pain clinics that place the emphasis not on eliminating pain but on helping patients to live with it. The first aim of these clinics is to restore patients to physical strength and health. Then comes a programme of practical advice on how best to live as normal a life as possible without exacerbating the pain. And then there is the more formal psychological help. It rarely removes the pain entirely but it does help most people to cope more effectively.

Do we really want to live in a world free of all pain any more than we seek to live in one free of risk? So addicted are we to the latter that we flock to theme parks to simulate the experience of danger and we even invent and pursue genuinely risky pastimes, from rock-climbing to parachuting.

So do we really want to abolish all pain? Certainly the masochist does not. And even those without the stomach to endure pain for themselves may turn up to see other people doing so. Performance art has featured artists who variously shoot, cut, trepan, pierce, scarify and burn themselves - and hold an audience while doing so. Clearly we are intent on eliminating pain from medicine. But eliminating it totally? Maybe not.

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