title: DEPERROR: Risks of systematic errors in drug and non-drug randomized clinical trials assessing intervention effects in patients with unipolar depression.
abstract: BACKGROUND
  Systematic errors in randomized clinical trials (RCTs) overestimate treatment effects. We systematically assessed the risks of bias in RCTs assessing the effects of drug and non-drug interventions for patients with unipolar depression.
  
  
  METHODS
  We searched bibliographic databases for drug and non-drug RCTs including patients with depression. We assessed the following risk of bias domains: sequence generation, allocation concealment, baseline imbalance, blinding, intention-to-treat analysis, selective outcome reporting, and funding. Risks of bias were compared for drug and non-drug trials and according to year of publication (before 1990; from 1990 to 1999; and 2000 to 2010).
  
  
  RESULTS
  Comparing drug trials (N=775) to non-drug trials (N=73), the proportion of drug trials with low risk of bias seemed superior regarding blinding of participants (p<0.001), blinding of health-care providers (p<0.001), and blinded outcome assessment (p<0.001). Non-drug trials were superior regarding sequence generation (p<0.001), allocation concealment (p=0.002), intention-to-treat analysis (p<0.001), and baseline imbalance (p=0.006). Adequate blinding of data managers (p=0.45), blinding of statisticians (p=0.69), and selective outcome reporting (p=0.55) did not differ. 41.5% of drug trials were funded by for-profit organizations compared to 12.3% of non-drug trials (p<0.001). In drug trials, the risk of bias decreased significantly over time. This did not reach statistical significance in non-drug trials.
  
  
  CONCLUSIONS
  This study only included trials published before 2010.
  
  
  CONCLUSIONS
  Included trials were associated with high risks of bias which may distort effect estimates. The risks of bias decreased with time for drug trials.
authors: Mental Health Centre Copenhagen, University of Copenhagen, Copenhagen, Denmark. Electronic address: jesper.krogh@regionh.dk.
authors: Jesper
authors: J
authors: Krogh
authors: Mental Health Centre Copenhagen, University of Copenhagen, Copenhagen, Denmark.
authors: Carsten Rygaard
authors: CR
authors: Hjorthøj
authors: The Copenhagen Trial Unit, Centre for Clinical Intervention Research, Department 7812, Rigshospitalet, Copenhagen University Hospital, Copenhagen, Denmark.
authors: Janus Christian
authors: JC
authors: Jakobsen
authors: The Copenhagen Trial Unit, Centre for Clinical Intervention Research, Department 7812, Rigshospitalet, Copenhagen University Hospital, Copenhagen, Denmark.
authors: Jane
authors: J
authors: Lindschou
authors: Mental Health Centre Copenhagen, University of Copenhagen, Copenhagen, Denmark.
authors: Lars Vedel
authors: LV
authors: Kessing
authors: Mental Health Centre Copenhagen, University of Copenhagen, Copenhagen, Denmark.
authors: Merete
authors: M
authors: Nordentoft
authors: The Copenhagen Trial Unit, Centre for Clinical Intervention Research, Department 7812, Rigshospitalet, Copenhagen University Hospital, Copenhagen, Denmark.
authors: Christian
authors: C
authors: Gluud
mesh_terms: D015982:Bias; D003863:Depression / Q000628:therapy*; D006801:Humans; D017063:Outcome Assessment, Health Care; D016032:Randomized Controlled Trials as Topic / Q000379:methods* / Q000592:standards; D012107:Research Design; D012306:Risk
keywords: Bias; Blinding; Depression; Effect estimates; Randomized clinical trials; Trial characteristics