title: To what extent are surgery and invasive procedures effective beyond a placebo response? A systematic review with meta-analysis of randomised, sham controlled trials.
abstract: OBJECTIVE
  To assess the quantity and quality of randomised, sham-controlled studies of surgery and invasive procedures and estimate the treatment-specific and non-specific effects of those procedures.
  
  
  METHODS
  Systematic review and meta-analysis.
  
  
  METHODS
  We searched PubMed, EMBASE, CINAHL, CENTRAL (Cochrane Library), PILOTS, PsycInfo, DoD Biomedical Research, clinicaltrials.gov, NLM catalog and NIH Grantee Publications Database from their inception through January 2015.
  
  
  METHODS
  We included randomised controlled trials of surgery and invasive procedures that penetrated the skin or an orifice and had a parallel sham procedure for comparison.
  
  
  METHODS
  Three authors independently extracted data and assessed risk of bias. Studies reporting continuous outcomes were pooled and the standardised mean difference (SMD) with 95% CIs was calculated using a random effects model for difference between true and sham groups.
  
  
  RESULTS
  55 studies (3574 patients) were identified meeting inclusion criteria; 39 provided sufficient data for inclusion in the main analysis (2902 patients). The overall SMD of the continuous primary outcome between treatment/sham-control groups was 0.34 (95% CI 0.20 to 0.49; p<0.00001; I(2)=67%). The SMD for surgery versus sham surgery was non-significant for pain-related conditions (n=15, SMD=0.13, p=0.08), marginally significant for studies on weight loss (n=10, SMD=0.52, p=0.05) and significant for gastroesophageal reflux disorder (GERD) studies (n=5, SMD=0.65, p<0.001) and for other conditions (n=8, SMD=0.44, p=0.004). Mean improvement in sham groups relative to active treatment was larger in pain-related conditions (78%) and obesity (71%) than in GERD (57%) and other conditions (57%), and was smaller in classical-surgery trials (21%) than in endoscopic trials (73%) and those using percutaneous procedures (64%).
  
  
  CONCLUSIONS
  The non-specific effects of surgery and other invasive procedures are generally large. Particularly in the field of pain-related conditions, more evidence from randomised placebo-controlled trials is needed to avoid continuation of ineffective treatments.
authors.affiliation: Samueli Institute, Alexandria, Virginia, USA.
authors.forename: Wayne B
authors.initials: WB
authors.lastname: Jonas
authors.affiliation: Samueli Institute, Alexandria, Virginia, USA.
authors.forename: Cindy
authors.initials: C
authors.lastname: Crawford
authors.affiliation: Department of Pain and Translational Symptom Science, School of Nursing, University of Maryland, Baltimore, Maryland, USA Department of Anesthesiology, School of Medicine, University of Maryland, Baltimore, Maryland, USA.
authors.forename: Luana
authors.initials: L
authors.lastname: Colloca
authors.affiliation: Program in Placebo Studies, Beth Israel Deaconess Medical Center, Harvard Medical School Boston, Massachusetts, USA.
authors.forename: Ted J
authors.initials: TJ
authors.lastname: Kaptchuk
authors.affiliation: The Methodist Hospital, Houston, Texas, USA.
authors.forename: Bruce
authors.initials: B
authors.lastname: Moseley
authors.affiliation: Department of Bioethics, Clinical Center, National Institutes of Health, Bethesda, Maryland, USA.
authors.forename: Franklin G
authors.initials: FG
authors.lastname: Miller
authors.affiliation: Department of Medical Psychology, University Medical Center Hamburg-Eppendorf, Hamburg-Eppendorf, Hamburg, Germany.
authors.forename: Levente
authors.initials: L
authors.lastname: Kriston
authors.affiliation: Institute of General Practice, Technische Universitat Munchen, Munich, Germany.
authors.forename: Klaus
authors.initials: K
authors.lastname: Linde
authors.affiliation: Institute of Medical Psychology, Ludwig-Maximilians-University Munich, Munich, Germany.
authors.forename: Karin
authors.initials: K
authors.lastname: Meissner
mesh_terms: D059350:Chronic Pain / Q000601:surgery*; D005764:Gastroesophageal Reflux / Q000601:surgery*; D006801:Humans; D015990:Placebo Effect; D016032:Randomized Controlled Trials as Topic
keywords: COMPLEMENTARY MEDICINE; INTERNAL MEDICINE; SURGERY