Effects of Expectancy and Mindfulness Instructions on Chronic Pain

Standard mindfulness of breath practice to last 15 minutes. Accompanied by either a positive or negative expectancy script directly beforehand.

Standard mindfulness of breath practice to last 15 minutes. Accompanied by either a positive or negative expectancy script directly beforehand.

Sham-mindfulness comparator to last 15 min. Participants will be prompted every 3 min to "take a deep breath, as we sit here in mindfulness." Accompanied by either a positive or negative expectancy script directly beforehand.

Sham-mindfulness comparator to last 15 min. Participants will be prompted every 3 min to "take a deep breath, as we sit here in mindfulness." Accompanied by either a positive or negative expectancy script directly beforehand.

Current pain intensity will be assessed using a 0-10 numeric rating scale, with 0 indicating no pain and 10 indicating the worst pain imaginable. Pain intensity will be assessed immediately before and after the intervention; the primary analysis will compare post-intervention ratings across experimental conditions while adjusting for the corresponding pre-intervention rating.

Current pain unpleasantness will be assessed using a 0-10 numeric rating scale, with 0 indicating not at all unpleasant and 10 indicating extremely unpleasant. Pain unpleasantness will be assessed immediately before and after the intervention; the primary analysis will compare post-intervention ratings across experimental conditions while adjusting for the corresponding pre-intervention rating.

Current anxiety will be assessed using a 0-10 numeric rating scale, with 0 indicating not at all anxious and 10 indicating extremely anxious. Anxiety will be assessed immediately before and after the intervention; analyses will compare post-intervention ratings across experimental conditions while adjusting for the corresponding pre-intervention rating.

Current desire for pain medication will be assessed using a 0-10 numeric rating scale, with 0 indicating no desire at all and 10 indicating the strongest possible desire. Desire for pain medication will be assessed immediately before and after the intervention; analyses will compare post-intervention ratings across experimental conditions while adjusting for the corresponding pre-intervention rating.

EEG frontal-midline theta power in the 4-8 Hz frequency band will be measured over a prespecified frontal-midline region of interest centered on Fz, FCz, and Cz. Mean theta power during the assigned exercise will be expressed relative to the 5-minute eyes-closed resting baseline.

State mindfulness will be assessed using the 3-item state version of the Metacognitive Processes of Decentering scale (MPoD-3). Scores will be assessed immediately before and after the intervention to characterize intervention-related changes in state mindfulness.

State self-transcendence will be assessed using the 3-item state version of the Nondual Awareness Dimensional Assessment (NADA-3). Scores will be assessed immediately before and after the intervention to characterize intervention-related changes in state self-transcendence.

Expected effectiveness of the mindfulness exercise for reducing pain will be assessed using a 0-10 numeric rating scale, with 0 indicating not at all effective and 10 indicating extremely effective.

Perceived credibility or believability of the exercise as a pain-management technique will be assessed using a 0-10 numeric rating scale, with 0 indicating not at all credible and 10 indicating extremely credible.

Participants will indicate whether they experienced an unpleasant or adverse experience during the intervention using a Yes/No item. Participants responding Yes will have the opportunity to provide a free-text description of the experience.

Perceived sociocultural features of the study encounter will be assessed using a 12-item exploratory questionnaire developed for this study. Participants will rate each item on a 1-7 Likert scale ranging from strongly disagree to strongly agree. The questionnaire includes four 3-item subscales assessing: (1) appeal to expert authority, (2) relational alliance-building, (3) ritualization of study procedures, and (4) co-constructed meaning-making. Higher scores on each subscale indicate greater perceived presence of that sociocultural scaffold.