Introduction
nausea, reduced pain, anxiety, pain
Placebo effects occur not only after placebo interventions, but also contribute to the overall effect of almost any treatmentAccording to the biopsychosocial model of arousal, stress integrates biological, psychological, and social factorsPlacebo effects are likewise based on mutual interactions between biological, psychological and social factors. Research has shown, for example, that placebo interventions trigger physiological responses, such as the release of endogenous opioids, resulting in reduced pain perceptionGiven the complex interplay between biological, psychological and cognitive factors in both the stress response and the placebo effect, it is reasonable to suppose that both phenomena can interfere with each other. For example, findings from placebo research in the field of pain suggest that placebo interventions decrease experimental pain by reducing anticipatory stress and anxietyIn a series of studies, we recently investigated placebo effects in an experimental nausea paradigm and could show that a suitable placebo intervention combined with verbal suggestions significantly reduced nausea and motions sickness in healthy volunteersIn this study, we investigated for the first time the effects of negative emotions induced by acute experimental stress on placebo effects in nausea using an established placebo nausea paradigmIn addition to nausea, we explored for the first time how acute stress and the placebo intervention might influence time estimation in nausea. The rationale for including time estimation as an outcome was based on previous findings that time perception is modulated by acute stress and anxiety