How expectation works: psychologic and physiologic pathways.
Although expectation has been the most widely studied of the mechanisms that drive the placebo effect, we still don't know how it works. We don't know how the thought that one will respond to a substance in a certain way is converted to symptom relief, intoxication, or airway resistance; the pathway between expectation of a response and the response itself remains uncharted. Nonetheless, in the last decade, brain-imaging studies have begun to uncover this pathway. This paper reviews both long-standing psychologic concepts about the underpinnings of expectation and some of the contemporary brain imaging research, which shows that when expectation alleviates depression, produces pain relief or improves parkinsonian symptoms, these effects come with relevant changes in brain activity and chemistry. These findings oblige us to reevaluate some of the traditional common sense notions of how expectation brings about its effects and how placebos work.
Clinical Professor of Psychiatry and Human Behavior, The Alpert Medical School of Brown University. He is the author of the book, The Placebo Effect in Clinical Practice, published by Oxford Press in 2012.
Walter A
WA
Brown
D006801:Humans; D010146:Pain / Q000188:drug therapy*; D059408:Pain Management / Q000379:methods*; D015990:Placebo Effect
brain imaging; expectation; placebo