Deceptive but not open label placebos attenuate motion-induced nausea.

OBJECTIVE: Nausea is a common complaint, known to respond to the placebo effect. Existing research has employed deception when administering placebos for nausea, limiting therapeutic translation on ethical grounds. We therefore examined the potential of non-deceptive open-label placebos (OLPs) to reduce nausea. METHODS: Galvanic Vestibular Stimulation (GVS) and Virtual Reality (VR) were employed to model nausea in healthy volunteers across two experiments. In both experiments nausea was elicited with and without sham treatment (peppermint vapor and brain stimulation, respectively). In Exp. 1, participants (n = 61) were randomized to deceptive placebo, semi-open placebo, fully-open placebo, or control. In Exp. 2, participants (n = 93) were randomized to deceptive placebo, semi-open placebo, or control. RESULTS: Exp. 1 found limited evidence for a placebo effect (F(1, 56) = 1.15, p = .29, ηp2 =0.02), even following deceptive treatment (F(1, 56) = 1.92, p = .17, ηp2=0.03). In Exp. 2, deceptive placebo reduced nausea relative to control (F(1, 89) = 6.91, p = .010, ηp2=0.07) and OLP (F(1, 89) = 5.47, p = .022, ηp2=0.06). Pooled Bayesian analysis across experiments provided strong evidence that deceptive placebos reduce nausea relative to control (BF10 = 30.91) and anecdotal evidence for the benefit of deceptive treatment over non-deceptive (BF10 = 2.46) and no benefit of OLP over control (BF10 = 0.63). CONCLUSIONS: No positive evidence for OLP effects in nausea were observed. However, a deceptive effect in VR was observed. These findings raise questions regarding the efficacy of open-label intervention in nausea.