Latent Inhibition Reduces Nocebo Nausea, Even Without Deception.

BACKGROUND: Nocebo nausea is a debilitating and prevalent side effect that can develop after conditioning occurs between cues present in the treatment context and the experience of nausea. Interventions that retard conditioning may therefore be able to reduce nocebo nausea. PURPOSE: To test whether 'latent inhibition', where pre-exposing cues in the absence of an outcome retards subsequent learning about those cues, could reduce nocebo nausea in healthy adults. METHODS: We examined this possibility using a Galvanic Vestibular Stimulation (GVS) model of nausea in healthy participants, with pre-exposure to the treatment cues achieved using a placebo version of GVS. RESULTS: In Experiment 1 we found clear evidence of conditioned nocebo nausea that was eradicated by latent inhibition following pre-exposure to placebo stimulation. Experiment 2 tested whether deception, which may be unethical in clinical settings, was necessary to produce latent inhibition by including an open pre-exposure group informed they were pre-exposed to placebo stimulation. Experiment 2 replicated the latent inhibition effect on nocebo nausea following deceptive pre-exposure from Experiment 1 and found that open pre-exposure was just as effective for reducing nocebo nausea. In both experiments, there was an interesting discrepancy found in expectancy ratings whereby expectations appeared to drive the development of conditioned nocebo nausea, but were not responsible for its suppression through latent inhibition. CONCLUSIONS: These findings have significant clinical implications. Applying open pre-exposure in clinical settings may effectively and ethically reduce the development of nocebo effects for nausea and other conditions via latent inhibition.