In a 3-week trial of 80 IBS patients, 59% given pills openly labelled placebo reported adequate relief, vs 35% given no pills. No deception was used.
Researchers handed IBS patients a bottle clearly labelled "placebo pills" and told them the capsules held nothing active. After three weeks, 59% of them reported adequate relief from their symptoms. In a matched group that got no pills, 35% did.
The trial, led by Ted Kaptchuk at Beth Israel Deaconess Medical Center and Harvard Medical School, was published in PLOS ONE in 2010. It tested a simple question: does a placebo still work if nobody is fooled?
How the trial worked
- 80 adults with irritable bowel syndrome (IBS) took part, from August 2009 to April 2010, at one academic medical centre in Boston.
- 37 were given open-label placebo pills: "placebo pills made of an inert substance, like sugar pills", in a bottle that said so, with the instruction to take 2 pills twice a day.
- The other 43 got no pills.
- Both groups had the same kind of visits, with the same amount of time and attention from the same clinicians.
What they found
- 59% vs 35%: the share reporting adequate relief at the 21-day endpoint, placebo group vs no-pill group.
- 92 points: how much the placebo group's symptom severity score improved from the start. The paper says a 50-point improvement "reliably indicates meaningful symptomatic improvement."
- The placebo group also scored higher on overall improvement at both the 11-day and 21-day checks.
The authors note that typical placebo responses in hidden, double-blind IBS drug trials run at 30 to 40%, so the 59% here was higher than usual. They suggest that knowing for certain you are getting the treatment being tested may itself help.
What it does not show
This was one small trial at one centre, over three weeks. Patients were told, in a hopeful way, that placebos have helped people with IBS through "mind-body self-healing processes", so the explanation may be part of the effect. The authors call it a "proof-of-principle" pilot study and say it needs repeating with more people and a longer follow-up. It is not a reason to stop any treatment. Talk to a doctor about IBS.
