Hypnosis increases heat detection and heat pain thresholds in healthy volunteers.

BACKGROUND AND OBJECTIVES: Hypnosis has been reported to induce analgesia and to facilitate anesthesia. To date, hypnotic-induced analgesia has had little explanation and it has even been questioned. The current study was thus designed to investigate the effect of hypnotic suggestion on thermal-detection thresholds, heat pain, and heat-pain tolerance thresholds. METHODS: In 15 healthy volunteers, enrolled in a randomized cross-over study, thermal thresholds were investigated in 2 sequences of measurements, under waking and hypnotic states, using a thermal stimulator. RESULTS: Heat detection and heat-pain thresholds were increased under hypnosis (from 34.3 +/-.9 degrees C to 36.0 +/- 2.9 degrees C and 45.0 +/- 3.7 degrees C to 46.7 +/- 2.7 degrees C, respectively, P <.05), whereas heat-pain tolerance and cold-detection thresholds were not statistically changed. CONCLUSION: These results indicate that hypnosis may partly impair the detection of A delta and C fibers stimulation, potentially explaining its analgesic effect.