Manon Houle

Date of Award


Degree Type


Degree Name

Doctor of Philosophy


The study evaluated the effects of expectation of analgesic efficacy on subsequent analgesic effectiveness for experimental and clinical pain. The experimental pain consisted of noxious heat pulses (45-51 C) delivered to the inside of the forearm. After providing baseline visual analogue scale ratings (VAS) of the sensory intensity and the unpleasantness of the heat pulses, sixty subjects were divided into two groups--a hi-expectancy group, made to expect a potent analgesic and a lo-expectancy group, made to expect an ineffective drug. In either case, half of each group received a potent analgesic while the other half received a placebo. Forty-five minutes after receiving the analgesic or placebo, subjects rated the thermal stimuli again. The results showed significant analgesic main effect for expectancy but no main effect for drug. Thus, the experimental effect that is attributable mainly to psychological mechanisms was more powerful than effects attributable to pharmacologic action. In the second phase, the powerful effects of expectation of analgesic efficacy were evaluated in the context of post-surgical pain following extraction of impacted teeth. In this case, the sixty subjects were told that they would receive the same drug as they had received in the experimental pain context. Forty-five additional subjects acted as controls--a hi-expectancy control (n = 15) group who believed they would receive a potent analgesic treatment, a lo-expectancy control (n = 15) who believed they would receive an inert substance and an unaltered expectancy group (n = 15) who received name brand Tylenol {dollar}\sp{lcub}\rm R{rcub}{dollar}3. In fact, all subjects received the pharmacological equivalent of Tylenol {dollar}\sp{lcub}\rm R{rcub}{dollar}3. After surgery, all subjects rated the sensory intensity and the unpleasantness of their post-surgical sensations over the course of 3 doses of the drug. The results demonstrated the robustness of the effects of expectancy in the course of recovery from surgical pain. Convergent evidence also pointed to the importance of expectancies in a clinical pain context. Hi-expectancies led to quicker return to work and reduced intake of narcotic and non-narcotic analgesics. The results are examined in light of the existing body of knowledge on pain perception and models of expectancy.



To view the content in your browser, please download Adobe Reader or, alternately,
you may Download the file to your hard drive.

NOTE: The latest versions of Adobe Reader do not support viewing PDF files within Firefox on Mac OS and if you are using a modern (Intel) Mac, there is no official plugin for viewing PDF files within the browser window.