You might think that people in pain simply imagine their improvement. Yet swellings can shrink, heart performance improve and constricted airways dilate - all thanks to the placebo response alone. What is going on here? And why is this remarkable happening steadfastly ignored by Western medicine? A recent groundbreaking conference on the "placebo response" - organised by the University of Westminster in London - has at last brought this biological mystery the attention it deserves.
The trouble is, the placebo effect is more than just an embarrassment to modern scientific medicine. It's a bombshell for our conventional notions of illness and disease. It reveals our capacity to modulate body symptoms and suffering in ways that can't be dismissed as "all in the mind".
The idea that mere "belief" can provoke observable physiological change "provokes a shudder of discomfort like a cold hand in the dark," remarks pain researcher Patrick Wall of St Thomas's Hospital, London. And no wonder: the demonstration that hope has the power to heal hardly fits the mechanistic models favoured by the medical establishment. It blurs that most well- defended of Western constructions: the boundary between mind and body, "psychological" and "physical".
The placebo response, once acknowledged, forces a merger between the "hard" world of objective scientific results with those messy realms of culture, social life and the individual psyche. It results from any action intended to heal - from any contact between doctor and patient or any procedure, such as admission to hospital, says Peter Fenwick, a neurophysiologist at the Institute of Psychiatry in London and the Radcliffe Infirmary in Oxford. "It flows from the interactions of patients with the circumstances they are in," he says. "It has already started, at the first contact with the doctor or healer."
Just the presence of culturally accepted "totems" or symbols of healing - diplomas on the wall, white coats, a clinic filled with impressive-looking equipment - can promote healing, says medical anthropologist Cecil Helman of Brunel University.
"The placebo response seems to depend in part on the creation of a particular ambience by the healer, whether it's a Harley Street specialist or a shaman in Latin America," he says.
Doctors' attitudes to their patients matter, too. To maximise the placebo effect, doctors need to "utilise a patient's belief system as an ally rather than an enemy," says Helman. In a nutshell, "don't treat them as meat, treat them as people," says David Reilly of the Glasgow Homeopathic Hospital. It's official: doctors can make us feel better just by being kind, sympathetic and hopeful. And the reverse is true, too. "Nocebos" are the opposite of placebos - the negative effects of belief on physical, mental and social health. People who experience insensitive or inappropriate treatment at the hands of medical practitioners can come away feeling worse.
Perhaps such negative experiences account, at least in part, for the growing popularity of alternative therapies - everything from reflexology and aromatherapy to homeopathy and crystal healing. The practitioners of these alternative therapies may often be better at exploiting the placebo response. Holistic healers typically take note of their clients' accounts and actively encourage them to believe that they can participate in their own healing, as Ursula Sharma, reader in social anthropology at the University of Keele, has documented.
But even within the mainstream, the placebo response is slowly becoming respectable, Fenwick claims, not least because it makes economic sense. "If we encouraged everything in the healing situation that can foster the response," he says, "the result would be shorter stays in hospital, less need for drugs and fewer complications."
Researchers are still struggling, however, to come to grips with how it works. Evidence is growing of the complex interconnections between our subjective experiences and the functioning of our immune and nervous systems. Already it is clear that stress and mood, for instance, can have profound effects on brain biochemistry; the mind can produce chemical changes in our bodies, says Fenwick.
Even relaxation can generate dramatic changes in bodily physiology, claims Herbert Benson of Harvard Medical School. He finds that the repetition of a prayer or some other meaningful form of words for half an hour or less can produce a "relaxation response" that may in itself have healing powers. Benson suspects this phenomenon may help to account for the miraculous cures reported in centres of spiritual pilgrimage such as Lourdes. Spontaneous remissions are part of the inherent capacity of individuals to heal themselves through biochemical pathways yet unknown. Fenwick agrees: such miracle cures really do happen, especially in cancers, he says.
Ranging from hard science to New Age mysticism, the London conference on the placebo response charted a concept in transition. In fact, some experts suspect we might be better off without it - so sullied is the term with overtones of quackery and imagined complaints. Even the Oxford English Dictionary gets it wrong, labelling the placebo as "a pill, medicine, procedure etc prescribed more for the psychological benefit to the patient of being given a prescription than for any physiological effect". Our premier wordsmiths find it difficult to shake off the deep-seated, but ultimately unhelpful distinction between mind and body.
"Placebo needs to lose its derogatory, negative connotations," Fenwick stresses. Some doctors still do not realise that it is a "gross error" to use a placebo to assess whether a patient's pain or disease is "real', and to dismiss the complaint on the basis of a placebo response. In reality, he points out, body and mind are inextricably intertwined, with the placebo response participating in every act of healing.
This realisation "adds to the most wonderful understanding of the nature of man," says Fenwick, as we begin to understand the importance of expectation and belief in the healing process. "Just think," Fenwick chuckles, "if we could identify this phenomenon and make it work we could do away with the medical profession"n