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Context matters! What is really tested in an RCT?
  1. Stefan Schmidt1,2
  1. 1 Department of Psychosomatic Medicine and Psychotherapy, Medical Center - University of Freiburg, Medical Faculty, University of Freiburg, Freiburg, Germany
  2. 2 Institut for Frontier Areas in Psychology and Mental Health, Freiburg, Germany
  1. Correspondence to Dr Stefan Schmidt, Dept. of Psychosomatic Medicine and Psychotherapy, Medical Center-University of Freiburg, 79104 Freiburg, Germany;{at}

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The American physician Henry Beecher was stationed in Italy during the Second World War and had to carry out surgery on wounded soldiers. When he ran out of morphine, a nurse suggested injecting the patients with a saline solution. The success of this deception was surprising and Beecher was so impressed that he put his later activities in the service of placebo research. His 1955 article, ‘The Powerful Placebo’,1 played a seminal role in the process of the randomised controlled trial (RCT) becoming the gold standard for determining the effectiveness of a treatment.2

Surprisingly, until today, it is not completely clear which factors lead to which effects in the two (or more) arms of an RCT. Let us start with what we know. If the patients are well randomised into two groups and receive exactly the same treatment except for an additional treatment in one of the groups (eg, a drug), then any difference between the two groups can be causally attributed to the additional treatment.

Meaningful comparisons

This difference in effect between groups is of high scientific value, as by means of an RCT, we have a methodological tool for identifying causal effects. However, from a patient’s individual perspective, the difference between groups is less interesting than another comparison, that is, the overall improvement from baseline to post treatment. The reason is that patients are primarily interested in the improvement and only second in the understanding why this treatment led to improvement. Most of the time, these two perspectives point to the same direction, but sometimes they do not. Consider, for example, the case of a large acupuncture trial with 1162 patients with chronic lower back pain.3 In this trial, the patients in the treatment arm underwent acupuncture needling at a set of well-chosen acupuncture points according to …

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  • Contributors SS is the sole author and has written everything by himself.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests None declared.

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