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Expectancy and Conditioning in Placebo Analgesia: Separate or Connected Processes?
Irving Kirsch1, Jian Kong2, Pamela Sadler3
1Harvard Medical School, Beth Israel Deaconess Medical Center, University of Plymouth.
Psychology of Consciousness (Washington, D.C.)
|August 6, 2014
Summary
Conditioning procedures reduce expected pain and enhance placebo analgesia by influencing pain expectations. This suggests expectancy mediates the impact of conditioning on pain relief, warranting further investigation into the indirect effect size.
Area of Science:
- Psychology
- Neuroscience
- Pain Management
Background:
- Placebo analgesia research often contrasts expectancy and conditioning as separate mechanisms.
- Conditioning procedures may influence pain perception by altering subjective expectations.
Purpose of the Study:
- To investigate the mediating role of expectancy in conditioning-induced placebo analgesia.
- To assess how conditioning affects expected pain and placebo pain reduction.
Main Methods:
- Participants received real or sham acupuncture, with instructions that treatment would be unilateral.
- Placebo effects were measured as the difference in pain between treated and untreated arm locations.
- Mediation analysis was employed to examine the relationship between conditioning, expectancy, and placebo analgesia.
Main Results:
- Conditioning significantly decreased expected pain in the treated location for both real and sham acupuncture groups.
- Conditioning enhanced placebo effects, increasing the difference in pain reports between treated and untreated sides.
- Mediation analysis indicated that expectancy may mediate the effects of conditioning on placebo analgesia.
Conclusions:
- Conditioning influences placebo analgesia, potentially through its effect on pain expectations.
- Expectancy appears to be a key mediator in the relationship between conditioning and placebo pain relief.
- Further research is needed to precisely quantify the indirect effect of conditioning on placebo analgesia via expectancy.
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