Expectancies and pain modulation

In the present study, the effects of negative and positive outcome expectations, induced by verbal suggestions, on conditioned pain modulation are studied. In a randomized controlled trial, participants will be allocated to one of three study groups: 1) an analgesia group where positive verbal suggestions are given; 2) a hyperalgesia group where negative verbal suggestions are given; or 3) a control group where no verbal suggestions are given. Participants will take part in one experimental test session. It is expected that the analgesia group will show an increased CPM effect compared to the control group and that the hyperalgesia group will show a decreased CPM effect compared to the control group following the verbal suggestions. Secondary outcomes include sex differences in the effects of expectations on CPM, the association between CPM and cognitive inhibition, and the effects of expectancy manipulation on other outcome parameters (e.g., pain ratings, psychophysiological assessments of heart rate and skin conductance levels and subjective stress).

The primary objective of the study is to investigate the role of expectations on conditioned pain modulation (CPM). Based on previous research it is expected that negative outcome expectations, induced by the verbal suggestion that a second painful stimulus will increase pain of the first painful stimulus, will decrease CPM efficacy and that positive outcome expectancies, induced by the verbal suggestion that a second painful stimulus will decrease pain of the first painful stimulus, will increase CPM efficacy compared to a control condition where no expectancies will be given. CPM will be assessed by the difference in pressure pain thresholds when assessed with and without a second painful stimulus, the cold pressor test.

As secondary objectives, sex differences in the role of expectations on CPM are assessed, the relationship between CPM and cognitive inhibition is examined and the effects of expectancy manipulation on other outcome parameters are assessed (e.g., pain ratings, psychophysiological assessments of heart rate and skin conductance levels and subjective stress). Finally, the role of psychological parameters are explored.

The study consists of one session lasting approximately 1 hour.

Positive outcome expectations will be induced by verbal suggestions. Participants will be told that they will experience either less or more pain or receive no instruction (the nature of the instructions varies depending on group allocation) during a second determination of pressure pain thresholds compared to a baseline assessment of pressure pain thresholds, as a result of the simultaneous immersion of the hand in cold water (cold pressor test).