title: Does psychotherapy work? An umbrella review of meta-analyses of randomized controlled trials.
abstract: To map and evaluate the evidence across meta-analyses of randomized controlled trials (RCTs) of psychotherapies for various outcomes.
  
  
  
  We identified 173 eligible studies, including 247 meta-analyses that synthesized data from 5157 RCTs via a systematic search from inception to December 2016 in the PubMed, PsycINFO and Cochrane Database of Systematic Reviews. We calculated summary effects using random-effects models, and we assessed between-study heterogeneity. We estimated whether large studies had significantly more conservative results compared to smaller studies (small-study effects) and whether the observed positive studies were more than expected by chance. Finally, we assessed the credibility of the evidence using several criteria.
  
  
  
  One hundred and ninety-nine meta-analyses were significant at P-value ≤ 0.05, and almost all (n = 196) favoured psychotherapy. Large and very large heterogeneity was observed in 130 meta-analyses. Evidence for small-study effects was found in 72 meta-analyses, while 95 had evidence of excess of significant findings. Only 16 (7%) provided convincing evidence that psychotherapy is effective. These pertained to cognitive behavioural therapy (n = 6), meditation therapy (n = 1), cognitive remediation (n = 1), counselling (n = 1) and mixed types of psychotherapies (n = 7).
  
  
  
  Although almost 80% meta-analyses reported a nominally statistically significant finding favouring psychotherapy, only a few meta-analyses provided convincing evidence without biases.
authors.affiliation: Department of Hygiene and Epidemiology, School of Medicine, University of Ioannina, Ioannina, Greece.|Department of Medical and Health Sciences, Pain and Rehabilitation Centre, Linköping University, Linköping, Sweden.
authors.forename: E
authors.initials: E
authors.lastname: Dragioti
authors.affiliation: Department of Hygiene and Epidemiology, School of Medicine, University of Ioannina, Ioannina, Greece.
authors.forename: V
authors.initials: V
authors.lastname: Karathanos
authors.affiliation: Department of Medical and Health Sciences, Pain and Rehabilitation Centre, Linköping University, Linköping, Sweden.
authors.forename: B
authors.initials: B
authors.lastname: Gerdle
authors.affiliation: Department of Hygiene and Epidemiology, School of Medicine, University of Ioannina, Ioannina, Greece.|Department of Epidemiology and Biostatistics, Imperial College London, London, UK.
authors.forename: E
authors.identifier: 0000-0002-5488-2999
authors.initials: E
authors.lastname: Evangelou
mesh_terms: D006801:Humans; D015201:Meta-Analysis as Topic; D017063:Outcome Assessment, Health Care / Q000706:statistics & numerical data*; D011613:Psychotherapy / Q000706:statistics & numerical data*; D016032:Randomized Controlled Trials as Topic / Q000706:statistics & numerical data*
keywords: meta-analysis; psychotherapy; randomized controlled trial; treatment