"Doctor, I have an earache."
2000 B.C.: "Here, eat this root."
1000 B.C.: "That root is heathen; say this prayer."
1850 A.D.: "That prayer is superstition; drink this potion."
1940 A.D.: "That potion is snake oil; swallow this pill."
1990 A.D.: "That pill is ineffective; take this biotechnologically engineered drug."
2000 A.D.: "That drug is artificial. Here, eat this root."

The placebo is one of the biggest mysteries of medicine — powdered mummy, crab's eyes, viper's flesh and pearls. These are some Medieval medicinal cures and few would question the fact that they worked as a placebo.

But how many drugs in modern science might also be ineffective? The U.S. Office of Technology Assessment estimates that only one fifth of modern medical treatments in common use have been proved effective. Modern placebo effects include prescribing antibiotics for colds and flu, evidence that placebo use still has a place in modern medicine.

A study by Baylor College of Medicine found that surgery carried out on people with osteoarthritis of the knee produced no better results than in dummy operations. Patients who underwent placebo surgery were as likely to report pain relief as those who underwent the real thing.

Recently, the reputation of placebos as a deceitful fraud has undergone a dramatic change. To alternative medical practitioners, the placebo response represents the self-healing forces produced by the mind-body connection.

The word placebo comes from the Latin, meaning "I will please", and by the 19th century, it was a medicine given "more to please than to benefit the patient," according to A.K. Shapiro, author of The Powerful Placebo: From Ancient Priest to Modern Physician.

Although it's not fully understood how placebos works, three major reasons may explain the effect. For many patients, taking a placebo causes the release of endorphins, opiate-like substances naturally produced by the brain in times of stress.