The Role of Expectations on Treatment Outcomes: From the Experimental Context to the Clinical Practice

Expectations greatly influence a wide range of perceptions, from vision to pain. The placebo effect is a striking demonstration of the influence of positive expectations on clinical outcomes, while the nocebo effect attests to the role of negative expectations. Research on placebo and nocebo responses permits to isolate the effect of expectations on treatment outcomes without confounders associated with the administration of active agents (e.g., the effect of the treatment, side-effects). Importantly, clinical studies have demonstrated that expectations have a similar role when associated with active treatments, showing that positive expectations can significantly boost treatment effectiveness (i.e., placebo-related effects), while negative expectations can abolish the effect (i.e., nocebo-related effects). Placebos and nocebos can therefore be seen as models to tackle specific hypotheses on the modulatory role of expectations, which can then be further tested in association with active interventions, in the clinical context. Our goal is to bridge the gap between lab-based placebo and nocebo research and more ecological studies conducted in the clinical context. Do expectations work in a similar way when modulated in the laboratory and real life? Are the findings consistent between the lab and the clinical context?

Achieving this goal will require investigating the role of expectations at different levels. The influence of expectations on treatment outcomes can be studied by directly modulating expectations in an experimental environment, inferring greater causality but having limited ecological validity. Expectations are also tested in clinical trials as predictors of active treatment success and by evaluating treatment outcomes and side effects associated with the placebo arm. Qualitative data can also be important for acquiring descriptively rich and ecologically sound data, allowing for an in-depth exploration of the role of expectations in the clinical setting. Altogether, results from these different types of research designs could contribute to gaining a better understanding of the role of expectations in modulating treatment outcomes both in lab-based studies and in the clinical context.

In this Research Topic, we aim to collect studies reporting new findings on the role of expectations on treatment outcomes across different contexts. Towards this end, we welcome submissions that report the latest research on the modulatory role of expectations in placebo and nocebo responses and their related effects - i.e., the effect of expectations on active treatments. We welcome a) basic science experimental designs, b) clinical trials, c) qualitative data, d) protocol studies, and e) narrative, systematic and scoping reviews, especially those bridging the gap between laboratory data and clinical findings.

With this collection reporting on expectancy-focused studies from different research contexts, we aim to advance our understanding of how to use the power of expectations in the clinical context to boost positive outcomes and limit negative effects.