Discussion
nausea, pain
MOTION SICKNESS
This is the first study to investigate the interplay between acute stress and placebo effects in nausea. In line with previous studiesUsing a visceral pain model, Roderigo et al.The question of whether placebo-induced expectations can affect peripheral physiological systems remains controversial. Although autonomic changes can be reliably induced by placebo interventionsIn an exploratory approach, we used time estimation as a novel and promising marker to monitor negative emotional statesThis is the first study to investigate the influence of acute stress on subjective and physiological placebo effects in nausea. We applied a randomized controlled, partially blinded design with behavioral, psychophysiological and humoral outcome variables and obtained a high internal validity of the results. Manipulation checks indicated successful induction of acute stress and positive expectations in the respective groups. Nonetheless, the study has several limitations. The relatively homogenous, female-only, young and healthy study population reduces the generalizability of the results. At the same time, variance in physiological placebo effects associated with sexIn summary, our results suggest that acute stress did not alter placebo effects on nausea and motion sickness. At the same time, stress appeared to interfere with the validity of the gastric NTT ratio to measure nausea and thus the gastric placebo effect, possibly by increasing normal gastric motility in the fasting state. Future studies should investigate whether placebo effects on the gastric NTT ratio can also be induced in the fed state and how acute stress alters placebo effects in such situations. In addition, the interplay between stress and placebo effects in nausea should also be investigated in healthy men as well as in patients, who are usually exposed to a variety of internal and external stressors.