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Randomized controlled trial · 2021

Open-label placebo vs double-blind placebo for irritable bowel syndrome: a randomized clinical trial

Lembo A, Kelley JM, Nee J, Ballou S, Iturrino J, Cheng V, Rangan V, Katon J, Hirsch W, Kirsch I, Hall K, Davis RB, Kaptchuk TJ

Pain, 2021 · PMID 33769362

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In short

The comparison the earlier trials were missing: open-label placebo tested directly against concealed double-blind placebo and against no pill.

Study type
Randomized controlled trial
Published
Pain, 2021
Topics
Open-label placebo, Double-blind placebo, Irritable bowel syndrome

open-label placebo vs double-blind placebo?

They performed about the same — in this 2021 IBS trial, openly labelled placebo and concealed double-blind placebo both beat no treatment, and did not differ significantly from each other. It is the strongest single trial that deception is not the operative ingredient.

Earlier open-label placebo trials compared pills to no pills. This one added the arm that matters most methodologically — a concealed placebo — so the effect of open labelling could be read against the conventional design.

The question

Does an openly labelled placebo perform differently from a concealed placebo in the same condition and protocol?

How it was done

  • 262 adults with irritable bowel syndrome randomized to open-label placebo, double-blind placebo, or no-pill control for six weeks.
  • Double-blind participants were told they might receive placebo or peppermint oil; open-label participants were told outright their pills were inert.
  • Primary outcome was change in IBS symptom severity.

What was reported

  • Both open-label placebo and double-blind placebo produced greater symptom-severity improvement than the no-pill control.
  • Open-label and double-blind placebo did not differ significantly from each other on the primary outcome.
  • The authors interpreted this as evidence that concealment is not required for the response.

Limitations

  • Single condition with subjective primary outcomes.
  • Six-week duration leaves durability unaddressed.
  • Recruiting people willing to enrol in a placebo trial may select for responsiveness.

Why it matters

This is the strongest single trial for the claim that deception is not the operative ingredient — and it is the study to cite when someone assumes open-label placebo is a weaker version of the real thing.

Citation

Lembo A, et al. Open-label placebo vs double-blind placebo for irritable bowel syndrome: a randomized clinical trial. Pain. 2021;162(9):2428–2435.

PMID 33769362

This summary is written by Efficacy Labs and is not a substitute for the original publication. The research described here is independent work by third parties and was not conducted using Efficacy Labs products. Efficacy Labs products contain no active therapeutic ingredient and are not intended as substitutes for prescribed medication or professional medical care. Information on this website is provided for general educational and research purposes and is not medical advice. References to published research describe independent scientific literature and do not imply that the research was conducted using Efficacy Labs products unless explicitly stated.

Background

What the placebo effect is, explained simply

How the effect is defined, what researchers think drives it, and how it is measured in trials like this one.

Products

Placebo pills for research and education

Inert capsules from Efficacy Labs, what they contain, and how to order them for a study or a classroom.

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