Article Text

Download PDFPDF

Implications of a complexity perspective for systematic reviews and guideline development in health decision making
  1. Mark Petticrew1,
  2. Cécile Knai1,
  3. James Thomas2,
  4. Eva Annette Rehfuess3,
  5. Jane Noyes4,
  6. Ansgar Gerhardus5,6,
  7. Jeremy M Grimshaw7,8,
  8. Harry Rutter1,9,
  9. Elizabeth McGill1
  1. 1 Faculty of Public Health and Policy, London School of Hygiene and Tropical Medicine, London, UK
  2. 2 EPPI-Centre, SSRU, Department of Social Science, UCL Institute of Education, University College London, London, UK
  3. 3 Institute for Medical Information Processing, Biometry and Epidemiology, Pettenkofer School of Public Health, LMU Munich, Munich, Germany
  4. 4 School of Social Sciences, Bangor University, Bangor, UK
  5. 5 Institut für Public Health und Pflegeforschung, Universität Bremen, Bremen, Germany
  6. 6 Department of Health Services Research, Institute for Public Health and Nursing Research, University of Bremen, Bremen, Germany
  7. 7 Clinical Epidemiology Program, Ottawa Hospital Research Institute, Ottawa, Canada
  8. 8 Department of Medicine, University of Ottawa, Ottawa, Canada
  9. 9 Department of Social and Policy Sciences, University of Bath, Claverton Down, Bath, UK
  1. Correspondence to Professor Mark Petticrew; Mark.Petticrew{at}


There is growing interest in the potential for complex systems perspectives in evaluation. This reflects a move away from interest in linear chains of cause-and-effect, towards considering health as an outcome of interlinked elements within a connected whole. Although systems-based approaches have a long history, their concrete implications for health decisions are still being assessed. Similarly, the implications of systems perspectives for the conduct of systematic reviews require further consideration. Such reviews underpin decisions about the implementation of effective interventions, and are a crucial part of the development of guidelines. Although they are tried and tested as a means of synthesising evidence on the effectiveness of interventions, their applicability to the synthesis of evidence about complex interventions and complex systems requires further investigation. This paper, one of a series of papers commissioned by the WHO, sets out the concrete methodological implications of a complexity perspective for the conduct of systematic reviews. It focuses on how review questions can be framed within a complexity perspective, and on the implications for the evidence that is reviewed. It proposes criteria which can be used to determine whether or not a complexity perspective will add value to a review or an evidence-based guideline, and describes how to operationalise key aspects of complexity as concrete research questions. Finally, it shows how these questions map onto specific types of evidence, with a focus on the role of qualitative and quantitative evidence, and other types of information.

  • complex interventions
  • systems
  • systematic reviews
  • public health

This is an open access article distributed under the terms of the Creative Commons Attribution-Non commercial IGO License (CC BY-NC 3.0 IGO), which permits use, distribution,and reproduction for non-commercial purposes in any medium, provided the original work is properly cited. In any reproduction of this article there should not be any suggestion that WHO or this article endorse any specific organization or products. The use of the WHO logo is not permitted. This notice should be preserved along with the article's original URL.

Statistics from

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.


  • Handling editor Soumyadeep Bhaumik

  • Contributors All authors contributed to discussions to decide on the content, and/or contributed examples and to revising and/or writing or reviewing the text, and approved the final version. MP is the guarantor.

  • Funding Funding provided by the World Health Organization Department of Maternal, Newborn, Child and Adolescent Health through grants received from the United States Agency for International Development and the Norwegian Agency for Development Cooperation.

  • Competing interests None declared.

  • Patient consent Not required.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Data sharing statement No additional data are available.