The Relationship Between Dissociated Measures of Inhibition and Hypnotic and Placebo Analgesia Effects.

Abstract

OBJECTIVE: The aim of the present research was to assess the relationship between the executive function of inhibition and hypnotic and placebo analgesia. METHODS: In a fully within-subjects experiment, 54 participants performed the Cold Pressor Task under 3 randomized conditions: (1) hypnotic analgesia; (2) placebo analgesia; and (3) a control condition. Pain threshold and pain tolerance were used as measures of pain perception in each condition. Analgesia was calculated by subtracting the control conditions from the 2 critical conditions (hypnosis and placebo). Following recent work indicating doubly-dissociated forms of inhibition, participants also completed: (1) the Stroop task; (2) the Hayling Sentence Completion Task (HSCT) and a matrix reasoning task, in a fixed order. RESULTS: Analyses revealed that both placebo analgesia (effect sizes rB >0.4) and hypnotic analgesia (effect sizes rB >0.7) suggestions were effective. The results also showed that HSCT performance predicted the magnitude of placebo pain threshold ( t(47) =3.448, p <.001, BF 10 =16.4), but not hypnotic pain threshold ( t(47) =0.537, p >.5, BF 01 =3.483). The results for placebo ( t(47) =3.126, p =.003) and hypnotic ( t(47) =0.295, p >.7) pain tolerance and HSCT performance were insensitive (BF 10 >0.3<3). Neither the Stroop task nor matrix reasoning scores predicted analgesic effects ( t s<1.6, p s>.1; BF 10 <0.3). CONCLUSION: The results highlight the efficacy of suggestion on pain perception and show a relationship between performance on the HSCT and the magnitude of the placebo effect. Limitations and directions for future research are discussed.