Revelation of a personal placebo response: its effects on mood, attitudes and future placebo responding

Abstract

While ethics of placebo use has been debated since discovery of the phenomena, there has yet to be a study that examines the aftereffect of individuals learning of a personal placebo response on their future ability to experience a placebo response. In the first study, eleven participants diagnosed with irritable bowel syndrome in a placebo study were interviewed individually about their personal placebo response. We found no changes in attitudes about the likelihood of using medical and non-medical treatments for pain, likelihood of participating in future studies or likeability and trust of experimenters. In addition, we found no changes in mood except for a slight improvement in frustration. In the second study, 77 undergraduate students from the University of Florida were divided into three conditions: placebo, control and repeated baseline. We used a double placebo design with verbal placebo suggestion and conditioning to induce a placebo response and to examine the effect of providing information about a participant's personal placebo response on their future placebo response. Using a heat thermode, we discovered that there were no differences in future pain responding between participants who were told that they experienced a placebo response versus those who were not. In addition, similar to the first study, we found no detrimental effects of the placebo information variables measured. These studies suggest the placebo response persists even after revelation of a personal placebo response and placebo use does not appear to cause adverse effects on mood and other attitude variables assessed.

Figure 1

A brief summary of the protocol for the placebo uninformed, placebo informed and repeated baseline groups in Study II.

Figure 2

Verification of the placebo effect through a comparison of the pain ratings between the repeated baseline and placebo groups in Study II with standard deviations. The lack of a significant (p<0.05) main effect for time for the repeated baseline group indicates that significant changes in pain ratings across time found for the placebo groups are most likely the result of our manipulations.

Figure 3

Pain ratings at baseline, time 1 and time 2 for the placebo informed and uninformed groups in Study II with standard deviations. While we found significant (p<0.05) changes across time between all time points for both placebo groups, we found no significant group differences between the placebo informed and uninformed groups at any time point.