Intended for healthcare professionals

Education And Debate

Why do we need randomised controlled trials to assess behavioural interventions?

BMJ 1998; 316 doi: (Published 14 February 1998) Cite this as: BMJ 1998;316:611
  1. Judith Stephenson (, senior lecturer in epidemiology,
  2. John Imrie, research fellow
  1. Department of Sexually Transmitted Disease, University College London Medical School, London WC1 6AU
  1. Correspondence to: Dr Stephenson
  • Accepted 21 July 1997

The value of the randomised controlled trial still generates debate.1 Although some of the earliest examples of these trials can be found in behavioural and psychosocial research, this is not an area that has adopted readily the randomised controlled trial to assess interventions.2 Two recent developments have intensified debate about the role of randomised controlled trials—the urgent need to find effective behavioural interventions against HIV 3 4 and the advance of evidence based medicine, which is moving the randomised controlled trial beyond clinical trials into areas such as health promotion. This article considers the merits and limitations of randomised controlled trials in the behavioural area compared with clinical medicine, and asks how these trials can be applied successfully to assess behavioural interventions.

Merits and limitations

The merits and limitations of randomised controlled trials in general have been widely discussed 5 6; only key points are repeated here. In clinical medicine, the randomised controlled trial is considered the best way of measuring the efficacy of interventions because of its ability to minimise bias and avoid false conclusions. Random assignment of individuals to different treatment groups is the best way of achieving a balance between groups for the known and unknown factors that influence outcome. This may seem to run counter to the traditional medical model of the doctor deciding which treatment is best for each patient, but it is considered ethical only when there is genuine uncertainty about which treatment to offer. By the same token, failure to tackle genuine uncertainty about treatments through randomised controlled trials can be considered unethical because it allows ineffective or harmful treatments to continue unchecked.


Aside from ethical issues, the limitations of randomised controlled trials are relative, and shared to some degree by other study designs. These include cost, feasibility, and relevance to the real …

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