Credibility of placebo transcutaneous nerve stimulation and acupuncture.

In a study comparing the credibility of acupuncture and sham transcutaneous nerve stimulation (TNS) within a group of chronic pain patients, equal suggestion of the sham TNS was achieved by incorporating a visual display and strong verbal suggestion into the placebo treatment. The analgesic effect of placebo is a confounding factor in controlled trials of physical methods of pain relief, and the use of sham therapy distinguishable from active therapy requires that the placebo be validated as a true control for the non-specific components that constitute the placebo aspect of the active treatment. This study uses a questionnaire designed to assess patient expectancy of effectiveness and concludes that sham TNS with strong visual and verbal suggestion may be a valid placebo for controlled studies of the analgesic effect of acupuncture.