Placebo interventions for all clinical conditions
Hrobjartsson and Gotzsche reviewed randomised placebo trials that also had a no-treatment group, searching five databases through March 2008. Of 234 included trials, 202 had usable outcome data, across 60 clinical conditions, and 16 were judged at low risk of bias. They report a small pooled effect on binary outcomes and a small pooled effect on continuous outcomes, larger for patient-reported than observer-reported outcomes, with effects for pain and nausea, very uncertain estimates for asthma and phobia, and no significant effect for a longer list of conditions. Larger effects were linked to physical placebos, small trials, trials studying placebo directly and trials that did not tell patients a placebo might be used. They considered pooling of continuous outcomes questionable and concluded that placebo interventions do not have important clinical effects in general, with possible effects on patient-reported outcomes that may partly reflect biased reporting.
Hrobjartsson and Gotzsche reviewed randomised placebo trials that also had a no-treatment group, searching five databases through March 2008. Of 234 included trials, 202 had usable outcome data, across 60 clinical conditions, and 16 were judged at low risk of bias. They report a small pooled effect on binary outcomes and a small pooled effect on continuous outcomes, larger for patient-reported than observer-reported outcomes, with effects for pain and nausea, very uncertain estimates for asthma and phobia, and no significant effect for a longer list of conditions. Larger effects were linked to physical placebos, small trials, trials studying placebo directly and trials that did not tell patients a placebo might be used. They considered pooling of continuous outcomes questionable and concluded that placebo interventions do not have important clinical effects in general, with possible effects on patient-reported outcomes that may partly reflect biased reporting.
Written from the abstract, Europe PMC record and Cochrane Library record, 2026-11-03.
What our sources record
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Hróbjartsson, A., & Gøtzsche, P. C. (2010). Placebo interventions for all clinical conditions. Cochrane Database of Systematic Reviews, 2010(1), CD003974. doi:10.1002/14651858.CD003974.pub3 https://doi.org/10.1002/14651858.CD003974.pub3