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


Kaptchuk et al. are surely correct in asserting the important contribution of warmth, attention,empathy and confidence to the placebo effect they demonstrate. But the converse must also be true: witholding these items is likely to have negative or deleterious effects on symptoms. Unfortunately this negative element was introduced into group 2 patients who were told: "practitioners introduced themselves and stated they had reviewed the patient’s questionnaire and "knew what to do." They then explained that this was "a scientific study" for which they had been "instructed not to converse with patients." This is likely to have falsely exaggerated the benefits of group 3 patients . Their results are therefore difficult to interpret.

It is worth emphasizing that the commonly held view that a placebo response is determined by psychological genesis is false. The placebo effect is highly complex, but evidence suggests it is effected via organic, possibly neuro- humoral mechanisms. The great error is to regard responders as sham, or fake, or to interpret symptoms that do respond as being psychogenic or non-organic.

Competing interests: None declared

Competing interests: No competing interests

02 May 2008
Emeritus Consultant Neurologist
Hull, UK Hu107bg