Intended for healthcare professionals

Education And Debate

Framework for design and evaluation of complex interventions to improve health

BMJ 2000; 321 doi: (Published 16 September 2000) Cite this as: BMJ 2000;321:694
  1. Michelle Campbell, senior policy analysta,
  2. Ray Fitzpatrick, professor of public health and primary care (,
  3. Andrew Haines, professor of primary health carec,
  4. Ann Louise Kinmonth, professor of general practiced,
  5. Peter Sandercock, professor of medical neurologye,
  6. David Spiegelhalter, senior scientistf,
  7. Peter Tyrer, professor of community psychiatryg
  1. a Office of the President, Medical Research Council of Canada, 1600 Scott Street, Ottawa, Ontario, Canada K1 OW9,
  2. b Division of Public Health and Primary Health Care, Institute of Health Sciences, University of Oxford, Oxford OX3 7LF,
  3. c Department of Primary Care and Population Sciences, Royal Free and University College Medical School, London NW3 2PF,
  4. d General Practice and Primary Care Research Unit, Department of Public Health and Primary Care, Institute of Public Health, Cambridge CB2 2SR
  5. e Neuroscience Trials Unit, Department of Clinical Neurosciences, Western General Hospitals NHS Trust, Edinburgh EH4 2XU
  6. f MRC Biostatistics Unit, Institute of Public Health, Cambridge CB2 2SR,
  7. g Department of Public Mental Health, Imperial College of Science, Technology, and Medicine, St Mary's Campus, London W2 1PD
  1. Correspondence to: R Fitzpatrick
  • Accepted 31 May 2000

Randomised controlled trials are widely accepted as the most reliable method of determining effectiveness, but most trials have evaluated the effects of a single intervention such as a drug. Recognition is increasing that other, non-pharmacological interventions should also be rigorously evaluated.1-3 This paper examines the design and execution of research required to address the additional problems resulting from evaluation of complex interventions—that is, those “made up of various interconnecting parts.”4 The issues dealt with are discussed in a longer Medical Research Council paper ( We focus on randomised trials but believe that this approach could be adapted to other designs when they are more appropriate.

Summary points

Complex interventions are those that include several components

The evaluation of complex interventions is difficult because of problems of developing, identifying, documenting, and reproducing the intervention

A phased approach to the development and evaluation of complex interventions is proposed to help researchers define clearly where they are in the research process

Evaluation of complex interventions requires use of qualitative and quantitative evidence

Challenges of trials of complex interventions

There are specific difficulties in defining, developing, documenting, and reproducing complex interventions that are subject to more variation than a drug. A typical example would be the design of a trial to evaluate the benefits of specialist stroke units. Such a trial would have to consider the expertise of various health professionals as well as investigations, drugs, treatment guidelines, and arrangements for discharge and follow up. Stroke units may also vary in terms of organisation, management, and skill mix. The active components of the stroke unit may be difficult to specify, making it difficult to replicate the intervention. The box gives other examples of complex interventions.

Examples of complex interventions

Service delivery and organisation:

Stroke units

Hospital at home

Interventions directed at health professionals' behaviour:

Strategies for implementing guidelines

Computerised decision support

Community interventions:

Community …

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