Placebo or Nocebo Interventions as Affected by Hypnotic Susceptibility

Abstract

The purpose of the present study was to examine placebo and nocebo effects under hypnotic analgesia in lowly hypnotizable (LH) and highly hypnotizable (HH) subjects. A placebo and nocebo, obtained in a two-step intervention (verbal expectation and conditioning), were studied in 12 LH and 12 HH subjects under hypnosis. Visual analog scales (VASs) of pain intensity were recorded in response to short, painful electrical stimuli. VAS scores of placebo-produced analgesia differed significantly from nocebo-produced hyperalgesia in the LH subjects. Placebo intervention combined with hypnotic analgesia in LH subjects led to an analgesic degree similar to that achieved in the HH subjects. Yet, no difference was detected between the placebo and the nocebo effects on the HH subjects. Expectations for placebo and nocebo were significantly higher in the LH subjects than in the HH subjects. It seems that the HH subjects were more “tuned” to an inner trait that made them less susceptible to contextual cues, and therefore, more resistant to placebo/nocebo interventions. The ability to achieve hypnotic analgesia in LH subjects to the degree reached in the HH subjects under combined placebo intervention and hypnosis induction is of clinical significance. Combining placebo intervention with the induction of hypnotic analgesia could markedly improve analgesia, regardless of the patients’ hypnotic susceptibility.