Placebo and nocebo effect in balancing ability

Different aspects of motor performance were shown to be malleable to placebo and nocebo influences. However, there are equivocal findings too, and in some cases, only perceived but not actual performance was impacted. Therefore, the present laboratory investigation aimed to study if postural stability is susceptible to placebo and nocebo effects. Driven by expectations, these effects could affect the motor stability of the elderly and people with motion instability.Participants (N=78) were randomized to a placebo, nocebo, or control group. We applied a sham sports cream with different (positive, negative, or neutral) instructions about its impact on postural stability. A modified version of the Modified Clinical Test of Sensory Interaction in Balance was used to assess actual postural stability with four different test types (standard, proprioceptive, visual, vestibular) before and after the intervention. Expected and perceived performance was measured with visual analog scales. We also assessed trait anxiety, the change in the state anxiety, optimism, holistic thinking, persistence, and the motivation to cooperate with questionnaires. The experimental manipulation did not significantly affect actual performance, and the assessed psychological trait, state variables, and expectations did not have an impact. Similarly, the experimental manipulation and the assessed psychological trait and state variables did not significantly affect perceived performance. However, a strong association (rho=0.627, p<0.001) was found between expectation and perceived performance.Based on our findings, postural stability is not susceptible to placebo and nocebo influences. However, there is a dissociation between actual (objective) and perceived (subjective) performance, where expectations impact perceived, not actual performance.