Placebo and Nocebo Effects as Bayesian-Brain Phenomena: The Overlooked Role of Likelihood and Attention

Author: Francesco Pagnini1, Diletta Barbiani2, Cesare Cavalera1, Eleanora Volpato1,3, Francesca Grosso1, Giacomo Andrea Minazzi1, Francesco Vailati Riboni1, Francesca Graziano4,5, Sonia Di Tella1, Gian Mauro Manzoni6, Maria Caterina Silveri1, Giuseppe Riva7,8, Deborah Phillips9
1 Department of Psychology, Università Cattolica del Sacro Cuore.
2 Department of Neurosciences, Biomedicine and Movement Sciences, University of Verona.
3 IRCCS Fondazione Don Carlo Gnocchi, Milan, Italy.
4 Bicocca Bioinformatics Biostatistics and Bioimaging B4 Center, University of Milano-Bicocca.
5 School of Medicine and Surgery, University of Milano.
6 Faculty of Psychology, eCampus University.
7 Applied Technology for Neuro-Psychology Lab, Istituto Auxologico Italiano IRCCS.
8 Humane Technology Lab., Catholic University of Milan.
9 Department of Psychology, Harvard University.
Conference/Journal: Perspect Psychol Sci
Date published: 2023 Jan 19
Other: Special Notes: doi: 10.1177/17456916221141383. , Word Count: 217

The Bayesian-brain framework applied to placebo responses and other mind-body interactions suggests that the effects on the body result from the interaction between priors, such as expectations and learning, and likelihood, such as somatosensorial information. Significant research in this area focuses on the role of the priors, but the relevance of the likelihood has been surprisingly overlooked. One way of manipulating the relevance of the likelihood is by paying attention to sensorial information. We suggest that attention can influence both precision and position (i.e., the relative distance from the priors) of the likelihood by focusing on specific components of the somatosensorial information. Two forms of attention seem particularly relevant in this framework: mindful attention and selective attention. Attention has the potential to be considered a "major player" in placebo/nocebo research, together with expectations and learning. In terms of application, relying on attentional strategies as "amplifiers" or "silencers" of sensorial information could lead to an active involvement of individuals in shaping their care process and health. In this contribution, we discuss the theoretical implications of these intuitions with the aim to provide a comprehensive framework that includes Bayesian brain, placebo/nocebo effects, and the role of attention in mind-body interactions.

Keywords: Bayesian brain; active inference; direct attention; mindful attention; mindfulness; mind–body; nocebo; placebo.

PMID: 36656800 DOI: 10.1177/17456916221141383