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.

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doi.org/10.1016/j.jmpt.2011.04.007, hdl.handle.net/1765/33678
Journal of Manipulative and Physiological Therapeutics
Erasmus MC: University Medical Center Rotterdam

de Groot, F.M, Voogt-Bode, A, Passchier, J, Berger, M.Y, Koes, B.W, & Verhagen, A.P. (2011). Headache: The placebo effects in the control groups in randomized clinical trials; An analysis of systematic reviews. Journal of Manipulative and Physiological Therapeutics, 34(5), 297–305. doi:10.1016/j.jmpt.2011.04.007