title: Complex interventions and their implications for systematic reviews: A pragmatic approach.
abstract: Complex interventions present unique challenges for systematic reviews. Current debates tend to center around describing complexity, rather than providing guidance on what to do about it. At a series of meetings during 2009-2012, we met to review the challenges and practical steps reviewer could take to incorporate a complexity perspective into systematic reviews. Based on this, we outline a pragmatic approach to dealing with complexity, beginning, as for any review, with clearly defining the research question(s). We argue that reviews of complex interventions can themselves be simple or complex, depending on the question to be answered. In systematic reviews and evaluations of complex interventions, it will be helpful to start by identifying the sources of complexity, then mapping aspects of complexity in the intervention onto the appropriate sources of evidence (such as specific types of quantitative or qualitative study). Although we focus on systematic reviews, the general approach is also applicable to primary research that is aimed at evaluating complex interventions. Although the examples are drawn from health care, the approach may also be applied to other sectors (e.g., social policy or international development). We end by concluding that systematic reviews should follow the principle of Occam's razor: explanations should be as complex as they need to be and no more.
authors: Department of Social & Environmental Health Research, London School of Hygiene & Tropical Medicine, London WC1H 9SH, United Kingdom. Electronic address: Mark.Petticrew@lshtm.ac.uk.
authors: Mark
authors: M
authors: Petticrew
authors: Washington State Institute for Public Policy, 110 Fifth Avenue SE, Olympia, WA, USA.
authors: Laurie
authors: L
authors: Anderson
authors: Centers for Disease Control and Prevention (CDC), Atlanta, GA, USA.
authors: Randy
authors: R
authors: Elder
authors: Institute of Population Health, University of Ottawa, Ottawa, Ontario, Canada.
authors: Jeremy
authors: J
authors: Grimshaw
authors: Centers for Disease Control and Prevention (CDC), Atlanta, GA, USA.
authors: David
authors: D
authors: Hopkins
authors: Centers for Disease Control and Prevention (CDC), Atlanta, GA, USA.
authors: Robert
authors: R
authors: Hahn
authors: Colorado School of Public Health, University of Colorado Denver, Denver, CO, USA.
authors: Lauren
authors: L
authors: Krause
authors: Institute of Population Health, University of Ottawa, Ottawa, Ontario, Canada.
authors: Elizabeth
authors: E
authors: Kristjansson
authors: Centers for Disease Control and Prevention (CDC), Atlanta, GA, USA.
authors: Shawna
authors: S
authors: Mercer
authors: Centers for Disease Control and Prevention (CDC), Atlanta, GA, USA.
authors: Teresa
authors: T
authors: Sipe
authors: Institute of Population Health, University of Ottawa, Ottawa, Ontario, Canada.
authors: Peter
authors: P
authors: Tugwell
authors: Canadian Cochrane Centre, Ottawa Hospital Research Institute, Ottawa, Ontario, Canada.
authors: Erin
authors: E
authors: Ueffing
authors: The McCaughey Centre, Melbourne School of Population Health, The University of Melbourne, Melbourne, Australia.
authors: Elizabeth
authors: E
authors: Waters
authors: Institute of Population Health, University of Ottawa, Ottawa, Ontario, Canada.
authors: Vivian
authors: V
authors: Welch
keywords: Complex interventions; Complexity; Evaluation; Evidence synthesis; Qualitative research; Systematic reviews