Headache: the placebo effects in the control groups in randomized clinical trials; an analysis of systematic reviews

J Manipulative Physiol Ther. 2011 Jun;34(5):297-305. doi: 10.1016/j.jmpt.2011.04.007. Epub 2011 May 19.


Objective: The purpose of this study is to describe the effects in the placebo and "no treatment" arms in trials with headache patients.

Method: This is a secondary analysis of randomized controlled trials from 8 systematic reviews and selected trials with a "no treatment" or placebo control group. The different types of "no treatment" and placebo interventions were assessed and classified into 6 subgroups. The analyses were carried out according to type of outcome variable.

Results: In total, 119 studies were included (7119 participants). The mean recovery rate in all control groups was 35.7%. Significantly more participants recovered in control groups of pharmacological studies than in nonpharmacological studies: 38.5% vs 15.0%, respectively. Adults were more likely to recover in nonpharmacological studies and children in pharmacological studies.

Conclusions: The mean recovery rate in the control groups was 36%. The recovery rate varied substantially between type of intervention and patients.

Publication types

  • Comparative Study

MeSH terms

  • Adult
  • Bias
  • Child
  • Control Groups
  • Cross-Over Studies
  • Headache / drug therapy
  • Headache / prevention & control
  • Headache / therapy*
  • Humans
  • Migraine Disorders / therapy
  • Placebo Effect*
  • Randomized Controlled Trials as Topic*
  • Recovery of Function
  • Risk
  • Tension-Type Headache / therapy
  • Waiting Lists