Placebo and nocebo effects as Bayesian brain phenomena: the overlooked role of likelihood and attention. 2022T42HSZ

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. The likelihood can be manipulated by paying attention to sensorial information. One form of attention seems particularly relevant here: mindful attention, as it is characterized by a reduction of priors influence and a focus on sensory information at the present moment. Moreover, attention can be consistent with the priors, or directed toward the opposite direction (inconsistent). The project aims to test if these forms of attention to sensorial information can modulate the mind-body interaction. This will be proved with a set of mind-body studies in which attention will be manipulated with quick attentive training promoting mindful or direct attention (either consistent or inconsistent with the priors). The impact of these training protocols will be tested in four different studies, involving general and clinical populations. The role of attention as a modulator of the mind-body effect will be tested for physical performance and sleep in the general population, and against clinical outcomes in hypertensive patients and patients with type 2 diabetes. All four studies will be randomized controlled trials exploring a mind-body effect along with manipulation of attention. Specifically, the proposal will focus on mindful attention to increase the precision of the likelihood and reduce the effects of the priors and on consistent and inconsistent direct attention to change the likelihood position and precision, hypothetically modulating the effects on the body. Potential neurological and psychological mechanisms will be explored, together with the possible role of mediators such as individual characteristics. Results will shed light on the role of attention in phenomena such as placebo/nocebo effects and push the boundaries of the current mind-body research. Attention may earn a spot, together with expectations and learning, as a main player in the placebo research. That implies an increased involvement of the individual in the care process, along with the opportunity to achieve an active role in shaping one’s own health, by leveraging these attentional strategies.