The brilliant study by Ted Kaptchuk et al 1 gives us extremely useful
insights in the components of the placebo effect. This research is
important, not least because it pertains to most areas of clinical
medicine. But it is also hugely complicated and confusing. One could, for
instance, argue that the results reveal not the impact of the placebo but
that of social desirability, a much neglected factor in this type of
investigation.
Put simply, social desirability describes the phenomenon that
patients who are treated with kindness and empathy may state that their
symptoms have improved when, in fact, they have not. This is dramatically
different from a placebo-effect, because it is not actually associated
with clinical improvement: the patient does not feel better but only
pretends to. But the results of clinical trials can nevertheless be
affected by the phenomenon 2.
In the study by Kaptchuk et al, the impressive difference in outcome
between the “limited” and the “augmented” group might be due to social
desirability. It is conceivable, I think, that patients receiving extra
warmth and attention returned that kindness to their therapist by
pretending they had improved while, in fact, they had not.
There is no easy way to control for social desirability in such
studies. One option would be to focus on objective endpoints - but this, I
am sure, would introduce other problems.
Prof. Ernst, MD, PhD, FRCP, FRCPEd
Complementary Medicine,
Peninsula Medical School,
Universities of Exeter & Plymouth
Reference List
(1) Kaptchuck TJ, Kelley JM, Conboy LA, Davis RB, Kerr CE, Jacobson
EE et al. Components of placebo effect: randomised controlled trial in
patients with irritable bowel syndrome. BMJ 2008;
doi:10.1136/bmj.39524.439618.25:1-8.
(2) Ernst E. Dissecting the therapeutic response. Swiss Med Wkly
2008; 138:23-24.
Competing interests:
None declared
Competing interests:
No competing interests
15 April 2008
Edzard Ernst
Director, Complementary Medicine
Peninsula Medical School, Universities of Exeter & Plymouth, 25 Victoria Park Road, Exeter, EX2 4NT
Rapid Response:
Placebo-effect or social desirability?
Dear Sir/Madam,
The brilliant study by Ted Kaptchuk et al 1 gives us extremely useful insights in the components of the placebo effect. This research is important, not least because it pertains to most areas of clinical medicine. But it is also hugely complicated and confusing. One could, for instance, argue that the results reveal not the impact of the placebo but that of social desirability, a much neglected factor in this type of investigation.
Put simply, social desirability describes the phenomenon that patients who are treated with kindness and empathy may state that their symptoms have improved when, in fact, they have not. This is dramatically different from a placebo-effect, because it is not actually associated with clinical improvement: the patient does not feel better but only pretends to. But the results of clinical trials can nevertheless be affected by the phenomenon 2.
In the study by Kaptchuk et al, the impressive difference in outcome between the “limited” and the “augmented” group might be due to social desirability. It is conceivable, I think, that patients receiving extra warmth and attention returned that kindness to their therapist by pretending they had improved while, in fact, they had not.
There is no easy way to control for social desirability in such studies. One option would be to focus on objective endpoints - but this, I am sure, would introduce other problems.
Prof. Ernst, MD, PhD, FRCP, FRCPEd
Complementary Medicine, Peninsula Medical School, Universities of Exeter & Plymouth
Reference List
(1) Kaptchuck TJ, Kelley JM, Conboy LA, Davis RB, Kerr CE, Jacobson EE et al. Components of placebo effect: randomised controlled trial in patients with irritable bowel syndrome. BMJ 2008; doi:10.1136/bmj.39524.439618.25:1-8.
(2) Ernst E. Dissecting the therapeutic response. Swiss Med Wkly 2008; 138:23-24.
Competing interests: None declared
Competing interests: No competing interests