Nocebo effects on pressure pain

Nocebo effects are known to adversely affect the experience of various physical symptoms, such as pain and itch. Recent studies have shown that nocebo effects can be experimentally induced and reduced by associative learning mechanisms of classical conditioning and counterconditioning, respectively, especially when combined with verbal suggestions. Prior pain conditioning studies have used heat or electrical pain to test nocebo pain manipulations in the lab. Nocebo conditioning and counterconditioning has, however, not been investigated for more clinically relevant pain modalities, such as pressure pain. Additionally, prior research has always used deception for inducing nocebo effects and open-label conditioning and counterconditioning have not been studied before. The aim of the current study is to investigate whether nocebo effects on pressure pain can be induced via open-label conditioning and reduced via open-label counterconditioning, combined with open-label verbal suggestions about the activation of a placebo Transcutaneous Electrical Nerve Stimulation (TENS) device.

The primary objective of the study is to investigate whether an induced nocebo effect can be effectively reduced by open-label counterconditioning, combined with open-label verbal suggestions, as compared to continued nocebo conditioning and extinction. To assess whether a nocebo effect is effectively reduced, the experimental (counterconditioning) and control (continued nocebo conditioning, extinction) groups will be compared on the change in the nocebo effect from before to after counterconditioning. The nocebo effect will be determined by calculating the mean difference between self-reported pain ratings during experimental trials and control trials from after nocebo conditioning to after counterconditioning. We expect participants in the counterconditioning and extinction groups to show a decreased nocebo effect, whereas we expect participants in the continued nocebo conditioning group to show no change or a slightly increased nocebo effect. Furthermore, we expect participants in the counterconditioning group to show a larger reduction of the nocebo effect than participants in the extinction group.
Secondary, we will investigate whether nocebo effects on pressure pain can be induced via open-label classical conditioning combined with open-label verbal suggestions in experimental (nocebo conditioning) as compared to a control (sham conditioning) group.

One lab session of approximately 2 hours. Aside from individual calibration of pressure pain intensities, participants will receive 4 non-painful pressure stimuli during practice session.
In each group, learning phase consists of a total of 20 trials with either moderately painful pressure stimuli (nocebo conditioning, continued nocebo conditioning), slightly painful pressure stimuli (extinction), or non-painful pressure stimuli (counterconditioning) in the experimental trials and slightly painful pressure stimuli in the control trials. In the control group (sham conditioning), participants will receive moderately painful and slightly painful stimuli in a randomized order. The test phase for all groups consists of 6 trials with slightly painful pressure stimuli presented in both experimental and control trials. The induction and reduction of nocebo effects will be analyzed using the self-reported pain levels in the testing phase.

5-10 minute breaks will be taken across different experimental parts (calibration, induction of nocebo effects, reduction of nocebo effects).

Open-label verbal suggestions about a placebo TENS device and open-label conditioning to induce and reduce nocebo effects on pressure pain, in the form of nocebo conditioning, continued nocebo conditioning, counterconditioning, and extinction.