Medical researcher Ted Kaptchuk wanted to see if it was possible to manipulate the placebo effect, so in a study sponsored by teh National Institutes of Health, he recruited 266 volunteers suffering from chronic arm pain which they rated at least a 3 on a 10-point scale.

Then he prescribed two types of fake medicines. 133 subjects received pretend acupuncture - the needles had retractable tips so they never penetrated the skin. The other 133 subjects were given a blue cornstarch pill.

25 percent of the acupuncture group experienced side effects from the nonexistent needle pricks, including 19 people who felt pain and 4 whose skin became red or swollen. 31 percent of the pill group experienced side effects from the make-believe drug, including dizziness, restlessness, rashes, headaches, nausea, and 4 cases of nightmares. Dry mouth and fatigue were the most common side effects, and 3 subjects withdrew from the study after reducing the dosage failed to control their symptoms. The reported side effects exactly matched those described by the doctors at the beginning of the study.

After 10 weeks, subjects taking sham pills said their pain decreased an average of 1.50 points on the 10-point scale. After 8 weeks, those receiving fake acupuncture reported a drop of 2.64 points. In other words, not receiving acupuncture reduces pain more than not taking drugs.

Kaptchuk chalks the results up to the ritual - acupuncture is more elaborate so patients think it works better.