Expectancy often predicts nausea, but the extent to which placebo interventions can alter nausea is less clear.
We conducted a systematic review to determine 1) if placebo interventions can affect nausea and 2) which features of these interventions are effective.
Articles were identified via PsychInfo, Medline, and PubMed databases. We targeted instructional and conditioning interventions aimed at altering nausea via the placebo effect.
Fourteen studies were identified, nine instructional and five conditioning. Many found evidence suggesting that placebo interventions could alter nausea, but a few found no evidence or ‘reverse’ effects. Effective interventions tended to be those that were aimed at participants with high initial expectancies, with evidence that combined or conditioning manipulations were more effective than instructions.
These findings suggest that placebo interventions can alter nausea and that these may serve as a useful way of reducing the burden of nausea in practice.