Considering bias and conflicts of interest among the included studies

Isabelle Boutron, Matthew Page, Julian P. T. Higgins, Douglas G Altman, Andreas Lundh, Asbjørn Hrõbjartsson, on behalf of the Cochrane Bias Methods Group

Research output: Chapter in Book/Report/Conference proceedingBook chapterEducationpeer-review


Bias can arise because of the actions of primary study investigators or because of the actions of review authors, or may be unavoidable due to constraints on how research can be undertaken in practice. Where possible, assessments of risk of bias in a systematic review should be informed by evidence. This chapter summarizes some of the key evidence about bias that informs our guidance on risk-of-bias assessments in Cochrane Reviews. Many results are often available in trial reports, so review authors should think carefully about which results to assess for risk of bias. Review authors who restrict their primary analysis in this way are encouraged to perform sensitivity analyses to show how conclusions might be affected if studies at a high risk of bias were included. The chapter also addresses how source of funding and conflicts of interest of study authors may impact on study design, conduct and reporting.

Original languageEnglish
Title of host publicationCochrane Handbook for Systematic Reviews of Interventions
EditorsJulian P. T. Higgins, James Thomas
Place of PublicationLondon
Publication date1. Jan 2019
ISBN (Print)9781119536628
ISBN (Electronic)9781119536604
Publication statusPublished - 1. Jan 2019


  • Cochrane reviews
  • Conflicts of interest
  • Funding sources
  • Review authors
  • Risk-of-bias assessments
  • Sensitivity analyses
  • Study design
  • Study reports
  • Systematic review
  • Trial reports


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