Response expectancies, treatment credibility, and hypnotic suggestibility: mediator and moderator effects in hypnotic and cognitive-behavioral pain interventions.

BACKGROUND Several studies have shown that response expectancies are an important mechanism of popular psychological interventions for pain. However, there has been no research on whether response expectancies and treatment credibility independently mediate hypnotic and cognitive-behavioral pain interventions and whether the pattern of mediation is affected by experience with the interventions. Also, past research has indicated that hypnotic pain interventions may be moderated by hypnotic suggestibility. However, these studies have typically failed to measure the full range of suggestibility and have assessed pain reduction and suggestibility in the same experimental context, possibly inflating the association between these variables. PURPOSE To clarify the mediator role of response expectancies and treatment credibility, and the moderator role of hypnotic suggestibility in the hypnotic and cognitive-behavioral reduction of pain. METHODS Approximately 300 participants were assessed for suggestibility. Then, as part of an apparently unrelated experiment, 124 of these individuals received analogue cognitive-behavioral, hypnotic, or placebo control pain interventions. RESULTS Response expectancies and credibility independently mediated treatment. The extent of mediation increased as participants gained more experience with the interventions. Suggestibility moderated treatment and was associated with relief only from the hypnotic intervention. CONCLUSIONS Response expectancies and treatment credibility are unique mechanisms of hypnotic and cognitive-behavioral pain interventions. Hypnotic suggestibility predicts relief from hypnotic pain interventions and this association is not simply an artifact of measuring suggestibility and pain reduction in the same experimental context. The relationship between suggestibility and hypnotic pain reduction appears to be linear in nature.