The effect of real and sham acupuncture on thermal sensation and thermal pain thresholds

OBJECTIVE: To compare the effect of real and sham acupuncture and a control intervention on thermal sensation and thermal pain thresholds. DESIGN: Single-blind, randomized controlled, repeated-measures trial. SETTING: Laboratory. PARTICIPANTS: Eighteen acupuncture-naive, healthy subjects with no history of upper-limb pathology or acupuncture contraindications. INTERVENTION: Subjects were randomly assigned (blind card allocation) to 1 of 6 possible orders of application of the interventions, which consisted of 25 minutes each of control, real, and sham acupuncture. MAIN OUTCOME MEASURES: Thermal sensation and thermal pain thresholds measured with a thermal sensory analyzer before and after each intervention. RESULTS: There were increases in cold and hot pain and cold sensation thresholds with real acupuncture. The level of increase did not differ significantly from the changes that occurred with sham acupuncture and control interventions. CONCLUSIONS: Although we observed a trend toward a decreased sensitivity to thermal pain and thermal sensation with real acupuncture, this trend did not differ significantly from the changes with control or sham interventions. Therefore, no support was provided for analgesic or placebo effects of acupuncture. The trend, combined with the relatively low power of the inferential tests applied does, however, suggest that further research is merited.