Analgesia for experimentally induced pain: multiple sessions of acupuncture compared to hypnosis in high- and low-susceptible subjects.

Repeated trials with cold-pressor pain were used to (a) determine whether the modest relation between hypnotic susceptibility and response to acupuncture analgesia obtained in previous experiments is enhanced over a series of treatments; (b) compare acupuncture and hypnotic analgesias; and (c) assess whether acupuncture analgesia increases with repeated treatments. Twenty high and 20 low hypnotically susceptible subjects participated on 5 different days. For half of each susceptibility group, Sessions 1-3 consisted of a baseline trial followed by an acupuncture analgesia trial. The remaining subjects had two no-treatment trials on each of these sessions. For all subjects Session 4 was a baseline followed by a hypnotic analgesia trial, and Session 5 was a repetition of the procedures followed in Sessions 1-3. Repeated exposures to acupuncture did not alter its analgesic effect in either susceptibility group; there were no instances of significant postacupuncture pain reduction. High susceptibles, but not low susceptibles, reported marked pain reduction after hypnotic analgesia. From these and previous findings it is concluded that the effect of acupuncture on experimentally induced pain is at best small and fragile.