Forskning
Udskriv Udskriv
Switch language
Region Hovedstaden - en del af Københavns Universitetshospital
Udgivet

Placebo response and effect in randomized clinical trials: meta-research with focus on contextual effects

Publikation: Bidrag til tidsskriftReviewForskningpeer review

DOI

  1. GRADE guidelines 32: GRADE offers guidance on choosing targets of GRADE certainty of evidence ratings

    Publikation: Bidrag til tidsskriftTidsskriftartikelForskningpeer review

  2. Infographic. Benefits and harms of exercise therapy in people with multimorbidity

    Publikation: Bidrag til tidsskriftKommentar/debatForskningpeer review

Vis graf over relationer

BACKGROUND: Contextual effects (i.e., placebo response) refer to all health changes resulting from administering an apparently inactive treatment. In a randomized clinical trial (RCT), the overall treatment effect (i.e., the post-treatment effect in the intervention group) can be regarded as the true effect of the intervention plus the impact of contextual effects. This meta-research was conducted to examine the average proportion of the overall treatment effect attributable to contextual effects in RCTs across clinical conditions and treatments and explore whether it varies with trial contextual factors.

METHODS: Data was extracted from trials included in the main meta-analysis from the latest update of the Cochrane review on "Placebo interventions for all clinical conditions" (searched from 1966 to March 2008). Only RCTs reported in English having an experimental intervention group, a placebo comparator group, and a no-treatment control group were eligible.

RESULTS: In total, 186 trials (16,655 patients) were included. On average, 54% (0.54, 95%CI 0.46 to 0.64) of the overall treatment effect was attributable to contextual effects. The contextual effects were higher for trials with blinded outcome assessor and concealed allocation. The contextual effects appeared to increase proportional to the placebo effect, lower mean age, and proportion of females.

CONCLUSION: Approximately half of the overall treatment effect in RCTs seems attributable to contextual effects rather than to the specific effect of treatments. As the study did not include all important contextual factors (e.g., patient-provider interaction), the true proportion of contextual effects could differ from the study's results. However, contextual effects should be considered when assessing treatment effects in clinical practice.

TRIAL REGISTRATION: PROSPERO CRD42019130257 . Registered on April 19, 2019.

OriginalsprogEngelsk
Artikelnummer493
TidsskriftTrials
Vol/bind22
Udgave nummer1
Sider (fra-til)493
ISSN1745-6215
DOI
StatusUdgivet - 26 jul. 2021

ID: 66949470