Meta-analysis · 2021
Effects of open-label placebos in clinical trials: a systematic review and meta-analysis
von Wernsdorff M, Loef M, Tuschen-Caffier B, Schmidt S
Scientific Reports, 2021 · PMID 33654150
In short
A pooled analysis of open-label placebo trials across conditions, reporting a positive overall effect alongside significant caveats about study quality.
- Study type
- Meta-analysis
- Published
- Scientific Reports, 2021
- Topics
- Open-label placebo, Evidence synthesis, Effect size
do open-label placebos work?
Probably, with caveats — pooling eleven randomized trials, this 2021 meta-analysis found a positive overall effect of openly labelled placebos in clinical populations, while flagging small samples, unblinded self-reported outcomes and possible publication bias.
Individual open-label placebo trials are small. This review pooled them to ask whether the pattern holds once the literature is looked at as a whole.
The question
Across published trials, do open-label placebos produce a measurable effect, and how reliable is that body of evidence?
How it was done
- Systematic search of randomized controlled trials of open-label placebo across clinical and non-clinical populations.
- Eleven trials met the inclusion criteria, covering conditions including irritable bowel syndrome, chronic pain, allergic rhinitis, depression and ADHD.
- Effect sizes were pooled and study quality and risk of bias were assessed.
What was reported
- A positive overall effect of open-label placebo was reported for clinical populations.
- Effects varied considerably by condition, outcome type and study design.
- The authors flagged small sample sizes and heterogeneity, and called for larger, better-controlled trials.
Limitations
- Small number of included trials, most with modest samples.
- Nearly all outcomes are self-reported and unblinded by design.
- Publication bias is difficult to rule out in a young literature.
Why it matters
If you read only one item in this library, read this one: it is the most honest summary of both the signal and the uncertainty in open-label placebo research.
Citation
von Wernsdorff M, Loef M, Tuschen-Caffier B, Schmidt S. Effects of open-label placebos in clinical trials: a systematic review and meta-analysis. Sci Rep. 2021;11:3855.
PMID 33654150This 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.
Continue reading
Randomized controlled trial
Open-label placebo in IBS (2010)
The trial that started modern open-label placebo research: patients were openly told their pills were inert placebos, and were still assessed against a no-treatment control.
Randomized controlled trial
Open-label placebo in chronic low back pain (2016)
An open-label placebo added on top of patients' existing treatment as usual for chronic low back pain, tested over three weeks in Portugal.
Randomized controlled trial
Open-label placebo and cancer-related fatigue (2018)
Cancer survivors with persistent fatigue took openly labelled placebo pills for three weeks alongside their usual care.