Indeed, a recent analysis of 46,000 heart patients, half of whom were taking a placebo, made the astonishing discovery that patients taking the placebo fared as well as those taking the heart drug. The only factor determining survival seemed to be a belief that the therapy will work and a willingness to follow it religiously.

Those who stuck to doctor's orders and took their pill three times a day fared equally well whether they were taking an active drug or just a sugar pill. Patients who tended not to survive were those who had been lax with their regimen, regardless of whether they had been given a placebo or an actual drug (BMJ, 2006; 333: 15-9).

Belief in the effectiveness of a drug-regardless of whether it is the 'true' drug or not-is enough to marshal the body's ability to heal.

The power of the placebo has been well illustrated in patients treated for Parkinson's disease, a motor-system disorder in which the body's mechanism for releasing the brain chemical dopamine is faulty. The standard treatment for Parkinson's is a synthetic form of dopamine. In a study carried out by the University of British Columbia in Canada, a team of doctors used PET scanning to demonstrate that, when patients given placebos were told they had received dopamine, their brain substantially increased the release of its own stores of the neurochemical (Science, 2001; 293: 1164-6).

In another dramatic example, at Methodist Hospital in Houston, Texas, Dr Bruce Moseley, a specialist in orthopaedics, recruited 150 patients with severe osteoarthritis of the knee and divided them into three groups. Two of the groups were given either arthroscopic lavage (which washed away any degenerative tissue and debris in the joint with the aid of an inserted viewing tube) or another form of debridement (which cleared out the joint using a tiny vacuum cleaner). The third group was given a sham operation: the patients were surgically prepared, placed under anaesthesia and wheeled into the operating room. Incisions were made in their knees, but no procedure was carried out.

Over the next two years-throughout which time none of the patients knew who had received the real operations and who had received the sham placebo treatment-all three groups of patients reported moderate improvements in pain and knee function. In fact, the placebo group reported better results than some of those who had been actually operated on (N Engl J Med, 2002; 347: 81-8).

The mental expectation of healing was enough to trigger the body's own healing mechanisms. The intention, brought about by the expectation of a successful operation, produced the physical changes. If the brain cannot distinguish between a thought and an action, would the body follow mental instructions to heal without the trick of a sugar pill? If I send my body a mental intention to calm down or speed up, will it listen to me? The literature on biofeedback and mind- body medicine says that it will.

Biofeedback
It was in 1961 that Neal Miller, a behavioural neuroscientist at Yale University, first proposed that people can be taught to mentally influence their autonomic nervous system, and control mechanisms such as blood pressure and bowel movements, much as a child learns to ride a bicycle.

Initially, he conducted a series of remarkable conditioning-and-reward experiments on rats. Miller discovered that, if he stimulated the pleasure centre in the brain, the rats could be trained to decrease their heart rate at will, control the rate at which urine filled their kidneys, even create different dilations of the blood vessels in each ear (J Comp Physiol Psychol, 1967; 63: 12-9; Science, 1969; 163: 434-45).