Author: Kirsch I1, Kong J2, Sadler P3, Spaeth R4, Cook A5, Kaptchuk T6, Gollub R2.
Affiliation: 1Harvard Medical School, Beth Israel Deaconess Medical Center, University of Plymouth. 2Harvard Medical School, Massachusetts General Hospital. 3Wilfrid Laurier University. 4Massachusetts General Hospital. 5Northwestern University. 6Harvard Medical School, Beth Israel Deaconess Medical Center.
Conference/Journal: Psychol Conscious (Am Psychol Assoc).
Date published: 2014 Mar
Other:
Volume ID: 1 , Issue ID: 1 , Pages: 51-59 , Word Count: 196
Abstract
Expectancy and conditioning are often tested as opposing explanations of placebo analgesia, most commonly by pitting the effects of a conditioning procedure against those of a verbally-induced expectation for pain reduction. However, conditioning procedures can also alter expectations, such that the effect of conditioning on pain might be mediated by expectancy. We assessed the effect of conditioning on expected pain and placebo-induced pain reduction. Participants were told that the treatment (real or sham acupuncture) would affect one side of the arm but not the other. Because a real acupuncture effect would not be specific to a randomly selected side of the arm, any difference in pain between the "treated" and the "untreated" side would be a placebo effect. There were no significant main effects or interactions associated with type of acupuncture (real versus sham). In both groups, conditioning decreased expected pain for "treated" location and also increased the placebo effect (i.e., the difference in pain report between "treated" and "untreated" locations). In addition, mediation analysis lent support to the hypothesis that the effects of conditioning on placebo analgesia may be mediated by expectancy, although the size of this indirect effect requires further study.
PMID: 25093194