WASHINGTON (Reuters) - Placebos can help patients feel better, even if they are fully aware they are taking a sugar pill, researchers reported on Wednesday on an unusual experiment aimed to better understand the “placebo effect.”

A pharmacist counts pills in a pharmacy in Toronto in this January 31, 2008 file photo. REUTERS/Mark Blinch/Files

Nearly 60 percent of patients with irritable bowel syndrome reported they felt better after knowingly taking placebos twice a day, compared to 35 percent of patients who did not get any new treatment, they report 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,” Ted Kaptchuk of Harvard Medical School and Beth Israel Deaconess Medical Center in Boston, who led the study, said in a statement.

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 percent to 40 percent 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 that it is just a sugar pill. Most people have assumed that a placebo will not work if the patient knows it is a placebo.

To test this common wisdom, Kaptchuk and colleagues enrolled 80 patients with irritable bowel syndrome or IBS, a chronic condition characterized by abdominal pain.

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,” Anthony Lembo, an IBS expert who worked on the study, said.

The study was funded by the National Center for Complementary and Alternative Medicine.