Towards an account of the placebo effect: a critical evaluation alongside current evidence

Abstract

This paper offers a critical analysis of several accounts of the placebo effect that have been put forward. While the placebo effect is most often thought of as a control in research and as a deceptive tool in practice, a growing body of research suggests that it ought to be thought of as a powerful phenomenon in its own right. Several accounts that aim to draw boundaries around the placebo effect are evaluated in relation to current evidence and it is argued that none of them adequately capture the variability and potency of the phenomenon. Two accounts, however, that point towards the underlying mechanisms of the placebo effect, are shown to offer promise in terms of developing a more comprehensive account of the placebo effect.

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Notes

  1. 1.

    I will use placebo effect and placebo response interchangeably in this manuscript.

  2. 2.

    Statistical regression can be accounted for by taking two baseline measures at the start of a trial.

  3. 3.

    Howick offers a modified version of Grünbaum’s account of the placebo effect, adding to the account a requirement that characteristic features are “features that are effective and not due to expectation effects” (Howick 2017, p. 1385). While this does help solve additional concerns that have been raised in relation to the account, primarily as it relates to placebo controls rather than placebo effects, it tends to exacerbate the worries raised here. On Howick’s account, determining what constitutes a placebo effect becomes even more difficult, since requiring that characteristic factors are effective means that classification of placebogenic and nonplacebogenic effects can take place only after one has examined the efficacy of each treatment component.

  4. 4.

    It’s worth noting that many of the accounts considered here were developed at a time when the mechanisms underlying the placebo effect were less well understood, so it is unsurprising that they sought to characterize the phenomenon in these ways.

  5. 5.

    Thank you to an anonymous reviewer for encouraging me to unpack this point in more detail.

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Acknowledgements

Many thanks to Peter Godfrey-Smith, Jesse Prinz, and John Greenwood for feedback on earlier versions of this manuscript. This work was partly supported by a Doctoral Award from the Social Sciences and Humanities Research Council of Canada (Grant No. 752-2015-0433).

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Friesen, P. Towards an account of the placebo effect: a critical evaluation alongside current evidence. Biol Philos 35, 11 (2020). https://doi.org/10.1007/s10539-019-9733-8

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Keywords

  • Placebo effect
  • Expectancy
  • Conditioning
  • Non-specific effects