title: Headache: the placebo effects in the control groups in randomized clinical trials; an analysis of systematic reviews.
abstract: OBJECTIVE
  The purpose of this study is to describe the effects in the placebo and "no treatment" arms in trials with headache patients.
  
  
  METHODS
  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.
authors.affiliation: Department of General Practice, Erasmus Medical Center, Rotterdam, The Netherlands.
authors.forename: Femke M
authors.initials: FM
authors.lastname: de Groot
authors.forename: Annieke
authors.initials: A
authors.lastname: Voogt-Bode
authors.forename: Jan
authors.initials: J
authors.lastname: Passchier
authors.forename: Marjolein Y
authors.initials: MY
authors.lastname: Berger
authors.forename: Bart W
authors.initials: BW
authors.lastname: Koes
authors.forename: Arianne P
authors.initials: AP
authors.lastname: Verhagen
mesh_terms: D000328:Adult; D015982:Bias; D002648:Child; D035061:Control Groups; D018592:Cross-Over Studies; D006261:Headache / Q000188:drug therapy / Q000517:prevention & control / Q000628:therapy*; D006801:Humans; D008881:Migraine Disorders / Q000628:therapy; D015990:Placebo Effect; D016032:Randomized Controlled Trials as Topic; D020127:Recovery of Function; D012306:Risk; D018781:Tension-Type Headache / Q000628:therapy; D014850:Waiting Lists