Focused analgesia and generalized relaxation produce differential hypnotic analgesia in response to ascending stimulus intensity

This study was designed in order to examine the effects of different types of hypnotic suggestion on hypnotic analgesia. Generalized relaxation and focused analgesia were induced in seven high-hypnotizable (HH) and eight low-hypnotizable (LH) subjects. Subjects were not aware to which group they belonged. The two groups did not differ in their expectation rates to achieve analgesia under hypnosis. Pain intensity and unpleasantness were rated on visual analogue scales in response to painful electrical stimuli, delivered in random order in five ascending intensities. Both focused analgesia and generalized relaxation decreased pain intensity significantly (P<0.01). However, stimulus-intensity response curves differed under the two hypnotic conditions. As stimulus intensity became higher pain reduction was enhanced under focused analgesia, while a constant reduction occurred under generalized relaxation. The interaction between hypnotic state and stimulus intensity was significant for focused analgesia (P<0.05) but not for generalized relaxation (P>0.07), difference became more pronounced when analyzed for HH subjects only (P<0.002 for analgesia, P>0.10 for relaxation). Pain reduction was significantly higher in HH than in LH subjects under focused analgesia (P<0.02) but not under generalized relaxation (P>0.5). We conclude that by utilizing two modes of hypnotic suggestions in response to ascending stimuli, we were able to discover two components of hypnotic analgesia. One shows a parallel shift in the stimulus-response function, has features similar to placebo and bears no clear relationship to hypnotic susceptibility. The other shows a slope change in the stimulus-response curve and has a positive relationship to hypnotic susceptibility.