Ethnocultural differences in the analgesic effects of placebo transcutaneous electrical nerve stimulation on cold-induced pain in healthy subjects: A preliminary study

Abstract

With the emphasis placed on placebo-controlled methodology in the testing of novel therapies, it is important that placebo effects are studied in their own right. Placebo effects, which may occur whenever a patient and a physician perceive a treatment as effective, may be susceptible to ethnocultural influences. However, experiments utilizing human subjects rarely take ethnocultural effects into account. This preliminary single-blind study examined the analgesic effects of placebo transcutaneous electrical nerve stimulation (TENS) on cold-induced pain in 24 healthy first-generation UK-born Asian and White Anglo-Saxon subjects. Pain threshold and pain intensity rating measurements were taken during six 10-min experimental cycles (two pre-, two during and two post-treatment) of the cold-induced pain test. A portable TENS unit with no current output was used to administer placebo TENS during the two treatment cycles. Two-way RM ANOVA performed on log transformed pain threshold and pain intensity data found significant effects for cycle ( P ≤0.01) and cycle x group interaction ( P ≤0.01). Further analysis found that Asian subjects produced a significantly greater increase in pain threshold and a significantly greater decrease in pain intensity rating during placebo TENS than White subjects. These findings suggest that ethnocultural background is an important determinant in placebo-induced analgesia in the laboratory setting. It is hoped that this preliminary study will serve to emphasize that ethnocultural factors should be considered during experiments utilizing human subjects.