How do I use placebo effects to improve my interventions? Harnessing Knowledge of Placebo Effects to Maximise the Effectiveness of Interventions in Sport.

Practitioners use treatments to help clients achieve their goals. Put simply, a placebo effect is a positive effect and a nocebo effect is a negative effect, which cannot be attributed to the active ingredients in the treatment. In short, it is a psychological effect. Unless such psychological effects are considered, the reason a treatment might succeed or fail could be due to a placebo or a nocebo effect. Placebo and nocebo effects can have powerful effects but are rarely captured in research or considered in practice. In the present chapter, we argue that practitioners and scientists should recognise, and indeed even embrace, the placebo and nocebo effects as active ingredients of a treatment that can enhance performance to a similar degree as, for example, self-efficacy. As such, and given that placebo and nocebo effects are often belief-based, an assessment of beliefs should be conducted before a treatment is delivered, and the role of beliefs examined as a possible reason for success or failure. Post-treatment, an interview should assess the extent to which beliefs are strengthened or weakened. Beliefs could be considered using self-efficacy theory and practitioners could seek to modify such beliefs via the four main self-efficacy sources. We argue that practitioners should look to develop positive beliefs in the effects of participating in an intervention and identify the proportion of change ascribed to the treatment and to beliefs.