Article Text

Download PDFPDF

Placebo effects in trials evaluating 12 selected minimally invasive interventions: a systematic review and meta-analysis
  1. Robin Holtedahl1,
  2. Jens Ivar Brox2,
  3. Ole Tjomsland3
  1. 1Fram Rehabilitation Centre, Bærum, Norway
  2. 2Department of Physical Medicine and Rehabilitation, Oslo University Hospital, Oslo, Norway
  3. 3South-Eastern Norway Regional Health Authority, Hamar, Norway
  1. Correspondence to Dr Robin Holtedahl; robi-hol@online

Abstract

Objectives To analyse the impact of placebo effects on outcome in trials of selected minimally invasive procedures and to assess reported adverse events in both trial arms.

Design A systematic review and meta-analysis.

Data sources and study selection We searched MEDLINE and Cochrane library to identify systematic reviews of musculoskeletal, neurological and cardiac conditions published between January 2009 and January 2014 comparing selected minimally invasive with placebo (sham) procedures. We searched MEDLINE for additional randomised controlled trials published between January 2000 and January 2014.

Data synthesis Effect sizes (ES) in the active and placebo arms in the trials’ primary and pooled secondary end points were calculated. Linear regression was used to analyse the association between end points in the active and sham groups. Reported adverse events in both trial arms were registered.

Results We included 21 trials involving 2519 adult participants. For primary end points, there was a large clinical effect (ES≥0.8) after active treatment in 12 trials and after sham procedures in 11 trials. For secondary end points, 7 and 5 trials showed a large clinical effect. Three trials showed a moderate difference in ES between active treatment and sham on primary end points (ES ≥0.5) but no trials reported a large difference. No trials showed large or moderate differences in ES on pooled secondary end points. Regression analysis of end points in active treatment and sham arms estimated an R2 of 0.78 for primary and 0.84 for secondary end points. Adverse events after sham were in most cases minor and of short duration.

Conclusions The generally small differences in ES between active treatment and sham suggest that non-specific mechanisms, including placebo, are major predictors of the observed effects. Adverse events related to sham procedures were mainly minor and short-lived. Ethical arguments frequently raised against sham-controlled trials were generally not substantiated.

This is an Open Access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/

View Full Text

Statistics from Altmetric.com

Supplementary materials

  • Supplementary Data

    This web only file has been produced by the BMJ Publishing Group from an electronic file supplied by the author(s) and has not been edited for content.

    Files in this Data Supplement:

Request Permissions

If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.