Patients with irritable bowel syndrome have added a further twist to the mystery of the placebo effect - where patients see relief in their symptoms despite being given a dummy drug.
A study has found that such placebos can work even when patients know they contain nothing more active than sugar.
The effect has long been recognised where a new drug is tested and a control group is given a dummy tablet that they too think is the active drug. It was thought the positive thinking of patients helps to relieve their symptoms.
However it now appears there is more involved than mere positive thinking with the “placebo effect”, as patients do not need to be deceived into thinking they are taking the active drug for it to work.
Participants experienced relief from irritable bowel syndrome (IBS) despite being told their medication was “like sugar pills” and contained no active ingredients.
At the end of the three-week trial, twice as many of the patients given the “dummy” pills reported loss of symptoms as those receiving no treatment at all.
Rates of improvement also doubled in the placebo group, an effect usually only associated with powerful IBS medications.
Study leader Dr Ted Kaptchuk, from Boston’s Harvard Medical School in the US, said: “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.
“We told the patients that they didn’t have to even believe in the placebo effect; just take the pills.
“These findings suggest that rather than mere positive thinking, there may be significant benefit to the very performance of medical ritual. I’m excited about studying this further. Placebo may work even if patients know it is a placebo.”
For the new study, 80 IBS patients were divided into two groups, one of which was asked to take a placebo pill twice a day for three weeks.
The results were published in the online journal Public Library of Science ONE.