Intended for healthcare professionals


Components of placebo effect: randomised controlled trial in patients with irritable bowel syndrome

BMJ 2008; 336 doi: (Published 01 May 2008) Cite this as: BMJ 2008;336:999

The Limits of Positivism

While the study by Kaptchuk et al demonstrates very clearly the power of non-specific aspects of treatments for conditions such as Irritable Bowel Syndrome, it is questionable whether they are really justified in drawing the conclusions that they do.

Their main hypothesis is that the non-specific aspects of treatment can be theoretically and practically separated into three distinct components: the patient’s response to observation and assessment, their response to the application of a ‘therapeutic ritual’ (the placebo) and their response to the quality of the professional’s interaction with them. They wish to be specific about the non-specifics. They interpret their results as confirming their hypothesis. Their fundamental assumption is that by putting the randomised patients through the three different pathways they describe, they are effectively observing the differential impact of these different elements. However, their study does not control for the question of intensity of involvement with the healer. As well as involving ‘the successive addition of the three postulated elements of the non-specific clinical interaction’, the three arms of the study also involve different levels of time spent engaging with the practitioner. An alternative interpretation of their results would be that non-specifics factors are important and the more that ‘happens’ in treatment situations, the better. Perhaps, the greater the level of involvement with the practitioner, the greater is the degree of trust, confidence and expectation generated.

But there is a deeper assumption at work in this research: that the non-specific aspects of treatment response can be investigated with the same positivist tools that are applied in research on the specific (technical) aspects. The researchers are attempting to break the non- specific dimension of treatment into separate ‘variables’ that can be controlled in empirical studies such as this. This is questionable. Moerman (2002) argues that we should move from talking about the ‘placebo effect’ and instead speak of the ‘meaning response’. What we are dealing with when we study the non-specific aspects of healing are the ways in which medical encounters always involve negotiations around meanings: the meaning of pain, sickness, healing and sometimes death. What we are dealing with is really the ‘art of healing’ (Gadamer, 1996).

Understanding a piece of art is always primarily an act of interpretation and only secondarily something that involves empirical investigation. Appreciating Picasso’s Guernica involves looking at it as a whole and understanding the context (political, cultural and personal) in which it was produced. We can only understand the various elements of the painting by first grasping how it works as a whole. If the non-specific aspects of medical treatments are indeed something approaching an art, it is questionable how far empirical studies underscored by a logic of positivism will get us.

Gadamer HG. The Enigma of Health. Stanford: Stanford University Press, 1996.

Moreman D. Meaning, Medicine and the ‘Placebo Effect’. Cambridge: Cambridge University Press, 2002.

Competing interests: None declared

Competing interests: No competing interests

29 May 2008
Pat Bracken
Professor of Philosophy, Diversity and Mental Health
University of central Lancashire, PR1 2HE