Can negative expectations increase pain and pain-related avoidance behavior?

Expectancy and avoidance behavior are thought to be one of the key mechanisms in the transition from acute to chronic pain. However, studies that directly evaluate the relationship between negative expectancy and avoidance are lacking. In this study, we investigate whether negative expectations can increase pain related avoidance behavior in healthy participants. Participants are assigned to either the nocebo group or control group, in which negative or no expectations regarding electrical pain stimuli are induced. A sham third electrode will act as the placebo device, and negative expectations are induced through verbal suggestions and conditioning (i.e., pairing certain color cues with high and medium intensity electrical pain stimuli). Avoidance behavior is measured through task selection (choosing to play a difficult game, rather than an easy game, in order to avoid high intensity stimulus).

Our research objectives are two-fold: First we investigate whether nocebo effects can be learned via electrical pain conditioning and verbal suggestions. We expect that participants in the nocebo group, but not the control group, will report higher pain ratings when seeing the conditioned cue (yellow or purple color), compared to the control cue during the nocebo test phase when the same intensity stimuli are given for these cues. Second, we investigate whether negative expectations induced via conditioning and verbal suggestions can increase avoidance behavior. We expect that participants in the nocebo group will select the avoidance task (playing a difficult game as opposed to an easy game) more than participants in the control group.

Exploratory hypothesis: We also assess several individual factors such as state anxiety, pain catastrophizing, pain vigilance, and fear of pain for exploratory analyses. We would like to investigate whether these individual factors 1. Moderate the relationship between negative expectancy and level of avoidance, 2. Correlate with induced pain expectations and 3. Moderate and mediate the nocebo effect.

1 session– 90-minute experiment.

Participants in the nocebo group receive a verbal suggestion stating that the third (sham) electrode will increase the intensity of the pain stimuli depending on the colors (conditioned cue) that are displayed on the screen. In addition, participants will receive a high intensity stimulus when they see the conditioned cue, and a medium intensity stimulus when they see the control cue during the acquisition phase, as part of the nocebo conditioning procedure. To assess avoidance, participants are asked to choose between playing an easy game or a difficult game which are paired with the color cues. The easy game is paired with the conditioned cue which was previously associated with the high intensity stimulus. The difficult game is paired with the control cue which was previously associated with the medium intensity stimulus. Therefore, participants must decide whether they want to play the easy game and receive a high intensity stimulus or avoid the high intensity stimulus by playing the difficult game.

Participants in the control group will not receive any verbal suggestions, and the high and medium stimuli are semi-randomized in that they are paired evenly with the color cues. Avoidance will also be assessed in participants in the control group. However, as the colors were not previously associated with a certain intensity, participants will not be influenced by the colors when selecting a game to play.