Placebos can help patients feel better, even if they are fully aware they are taking one, researchers reported.
With an unusual experiment, they aimed to better understand the "placebo effect."
Nearly 60% of patients with irritable bowel syndrome reported they felt better after knowingly taking placebos twice a day, compared to 35% of patients who did not get any new treatment, the research team reported in the Public Library of Science journal PLoS ONE.
"Not only did we make it absolutely clear that these pills had no active ingredient and were made from inert substances, but we actually had 'placebo' printed on the bottle," Dr Ted Kaptchuk of Harvard Medical School and Beth Israel Deaconess Medical Centre in Boston, who led the study, said in a statement.
Documenting the placebo effect
The placebo effect has been documented almost since the beginning of medicine.
Placebos are also vital to research on new drugs or treatments, and in general scientists have documented that 30% to 40% of patients will report feeling better or will show documented improvement of symptoms even when unknowingly taking a placebo.
But it is considered unethical to give a patient a placebo as part of standard medical treatment and not tell them. Most people have assumed that a placebo will not work if the patient knows it is a placebo.
To test this common wisdom, Dr Kaptchuk and colleagues enrolled 80 patients with irritable bowel syndrome.
The volunteers were recruited for a "mind-body" study, given placebo or nothing for three weeks and carefully monitored. Those given placebos were reminded they were taking inert pills.
"I felt awkward asking patients to literally take a placebo. But to my surprise, it seemed to work for many of them," Dr Anthony Lembo, an IBS expert who worked on the study, said.
The study was funded by the National Centre for Complementary and Alternative Medicine.
(Reuters Health, Maggie Fox, December 2010)