For years, placebos have been valued for their supposed ability to do nothing — unlike medications with active ingredients, placebos derive their healing ability psychologically, by fooling patients into thinking they're receiving a "real" drug.

However, a new study shows that placebos can offer effective treatment even when patients know they're taking a so-called "dummy pill."

Among patients with irritable bowel syndrome (IBS), 59 percent of those who knowingly took a placebo pill said their symptoms were adequately relieved after three weeks, while just 35 percent of patients who took no pills reported such relief.

"We were surprised by how effective the placebo pills were," said study researcher Ted Kaptchuk, an associate professor of medicine at the Harvard Medical School.

In most drug studies, a treatment that works 20 percent better than the control is seen as statistically significant and clinically meaningful. "But here, you have something that is almost two-folds better," Kaptchuk said.

In fact, the study showed the effects of the placebo pills were comparable to the effects of the powerful, but risky, IBS medication alosetron (sold under the brand name Lotronex).

"And most importantly, the placebo pills worked even when the patients know they were taking placebo pills and not real drugs," Kaptchuk told MyHealthNewsDaily.

The researchers gave 80 patients with irritable bowel syndrome two treatments. One group, the control group, received only consultations with doctors and nurses. The second group received the same consultations and inert microcyrstalline cellulose pills, which were clearly labeled as "placebos," and were told to take them twice a day.

Other placebo researchers said the results were interesting.

"Our current understanding is that, in order for placebos to work, patients have to believe strongly that the placebo is a real, active drug," said Damien Finniss, a researcher at the University of Sydney who was not involved in this study.

"But this challenges our thinking. This shows that some form of placebo effect still exists, and can still have a powerful positive effect, even when patients know they're not taking an active drug," Finniss said.

Kaptchuk said he and and his colleagues conducted the study when a previous study showed that as many as 50 percent of American physicians gave placebos to unsuspecting patients because patients respond so well to them.

"All too often, patients in clinical trials worry that when they're given the placebo, they won't receive proper treatment. We want to learn more about placebos, and this is our way of measuring the effects with total transparency, trust and informed consent," Kaptchuk said.

However, Kaptchuk said that while more research will be needed to replicate the findings in a larger group of patients, the study has advanced placebo research.

"Armed with this knowledge, we now know that we can measure the power of placebos in a responsible way in future trials and treatments, without having to deceive the patients and leading them on."

The findings were published today (Dec. 22) in the journal PLoS ONE.

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