Background: Placebo treatment can significantly influence subjective symptoms.  However, it is widely believed that response to placebo requires concealment or deception.  We tested whether open-label placebo (non-deceptive and non-concealed administration) is superior to a no-treatment control with matched patient-provider interactions in the treatment of irritable bowel syndrome (IBS).

Methods: Two-group, randomised, controlled 3-week trial (Aug 2009-Apr 2010) conducted at a single academic centre, involving 80 primarily female (70%) patients, mean age 47 +/- 18 with IBS diagnosed by Rome III criteria and with a score of 150 or higher on the IBS Symptom Severity Scale (IBS-SSS).  Patients were randomised to either open-label placebo pills presented as 'placebo pills made of an inert substance, like sugar pills, that have been shown in clinical studies to produce significant improvement in IBS symptoms through mind-body self-healing processes' or no-treatment controls with the same quality of interaction with providers.  The primary outcome was IBS Global Improvement Scale (IBS-GIS).  Secondary measures were IBS Symptom Severity Scale (IBS-SSS), IBS Adequate Relief (IBS-AR) and IBS Quality of Life (IBS-QoL).

Findings: Open-label placebo produced significantly higher mean (+/- SD) global improvement scores (IBS-GIS) at both 11-day midpoint (5.2 +/- 1.0 vs 4.0 +/- 1.1, p less than 0.001) and at 21-day endpoint (5.0 +/- 1.5 vs 3.9 +/- 1.3, p = 0.002).  Significant results were also observed at both time points for reduced symptom severity (IBS-SSS, p = 0.008 and p = 0.03) and adequate relief (IBS-AR, p = 0.02 and p = 0.03); and a trend favouring open-label placebo was observed for quality of life (IBS-QoL) at the 21-day endpoint (p = 0.08).

Conclusions: Placebos administered without deception may be an effective treatment for IBS.  Further research is warranted in IBS, and perhaps other conditions, to elucidate whether physicians can benefit patients using placebos consistent with informed consent.

Trial Registration: ClinicalTrials.gov NCT01010191.