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Cited by 150Pain Management and Placebo EffectStatistical Methods in Clinical TrialsMeta-analysis and systematic reviews

Placebo effect studies are susceptible to response bias and to other types of biases

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Hróbjartsson, Asbjørn, Kaptchuk, Ted J., Miller, Franklin G.·2011·Journal of Clinical Epidemiology
DOI 10.1016/j.jclinepi.2011.01.008PMC PMC3146959
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Abstract

Objective Investigations of the effect of placebo are often challenging to conduct and interpret. The history of placebo shows that assessment of its clinical significance has a real potential to be biased. We analyze and discuss typical types of bias in studies on placebo.Study design and setting A methodological analysis and discussion.Results The inherent nonblinded comparison between placebo and no-treatment is the best research design we have in estimating effects of placebo, both in a clinical and in an experimental setting, but the difference between placebo and no-treatment remains an approximate and fairly crude reflection of the true effect of placebo interventions. A main problem is response bias in trials with outcomes that are based on patients' reports. Other biases involve differential co-intervention and patient dropouts, publication bias, and outcome reporting bias. Furthermore, extrapolation of results to a clinical settings are challenging because of a lack of clear identification of the causal factors in many clinical trials, and the nonclinical setting and short duration of most laboratory experiments.Conclusions Creative experimental efforts are needed to assess rigorously the clinical significance of placebo interventions and investigate the component elements that may contribute to the therapeutic benefit.

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  • Because of causal indeterminacy, comparing different kinds of control conditions is not a valid way to determine whether placebo effects are present.

    “Due to causal indeterminacy, one cannot simply compare different types of control conditions to infer the presence or absence of placebo effects.”

    From Reevaluating the effectiveness of n-back training on transfer through the Bayesian lens: Support for the null (2016) · cites this paper as Hróbjartsson, Kaptchuk, and Miller (2011)

    The Introduction says that assessing a placebo effect requires comparison with a suitable control group, and the Conclusion calls placebo-versus-no-treatment comparison the best available design for estimating placebo effects. The section on extrapolation uses ‘causal indeterminateness’ to describe difficulty isolating the factors responsible for an observed effect, not to rule out control-group comparisons. The paper cautions that such comparisons are crude and susceptible to bias, but does not deem them invalid for detecting placebo effects. (LLM, conf=0.83)

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  • A true placebo-control trial presumably isolates the treatment's causal mechanism through the placebo condition, but comparing a placebo control with a no-contact control does not do this.

    “In true placebo-control trials, the causal mechanism of the treatment is presumably isolated by virtue of including the placebo control condition.However, the same is not true when comparing a placebo-control with a no-contact control.”

    From Reevaluating the effectiveness of n-back training on transfer through the Bayesian lens: Support for the null (2016) · cites this paper as Hróbjartsson et al., 2011

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Authors
Hróbjartsson, A., Kaptchuk, T. J., & Miller, F. G.
Affiliations
  • Rigshospitalet (DK)
  • Beth Israel Deaconess Medical Center (US)
  • National Institutes of Health (US)
Corresponding author
Hróbjartsson, Asbjørn
ORCID
Venue
Journal of Clinical Epidemiology
Publisher
Elsevier BV
Published
2011-11
Volume
64
Issue
11
Pages
1223-1229
ISSN
0895-4356 (ISSN-L)
DOI
10.1016/j.jclinepi.2011.01.008
PMC
PMC3146959
OpenAlex
W2097618916
Cited by
150
References
44
Citations by year
2026: 3 · 2025: 10 · 2024: 6 · 2023: 7 · 2022: 12 · 2021: 6 · 2020: 10 · 2019: 11 · 2018: 10 · 2017: 12 · 2016: 12 · 2015: 7 · 2014: 8 · 2013: 22 · 2012: 11
FWCI
6.98
Type
journal article
Language
en
Open access
Licence
Locations
  • Journal of Clinical Epidemiology (publishedVersion)
  • PubMed (publishedVersion)
  • PubMed Central (acceptedVersion)
  • Research at the University of Copenhagen (University of Copenhagen) (submittedVersion)
Funders
  • National Institutes of Health (Z99CL999999)
  • National Center for Complementary and Alternative Medicine
  • National Center for Complementary and Integrative Health (K24AT004095)
Topics
  • Life Sciences › Neuroscience › Cognitive Neuroscience › Pain Management and Placebo Effect
  • Physical Sciences › Mathematics › Statistics and Probability › Statistical Methods in Clinical Trials
  • Social Sciences › Decision Sciences › Statistics, Probability and Uncertainty › Meta-analysis and systematic reviews
Keywords
placebo effect, response bias, bias in clinical trials, patient-reported outcomes, patient dropout, publication bias, selective reporting
MeSH terms
Humans, Magnetic Resonance Imaging, Patient Dropouts, Placebos, Research Design, Bias, Placebo Effect, Randomized Controlled Trials as Topic, Treatment Outcome, Publication Bias, Research Subjects, Positron-Emission Tomography

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