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

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.