Induction of nocebo effects by verbal suggestions during the caloric test

Author

Abbey Weist, James Madison UniversityFollow

Creative Commons License

This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License.

Date of Graduation

5-7-2020

Document Type

Dissertation

Degree Name

Doctor of Audiology (AuD)

Department

Department of Communication Sciences and Disorders

Advisor(s)

Erin G. Piker

Jessica Irons

Melissa Garber

Abstract

The caloric test is the most frequently performed vestibular diagnostic test and is considered the “gold-standard” for the assessment of the peripheral vestibular system. Using a warm or cool stimulus, the caloric test alters the temperature gradient in the vestibular system resulting in nausea and dizziness. The nocebo effect is a phenomenon that can occur when negative expectations result in negative effects. No study has examined whether expectations of nausea and dizziness during the caloric test enhance the experience of unwanted symptoms. The purpose of this investigation was to determine whether a nocebo response can be elicited during the caloric test. Fifty-four participants between the ages of 18-26 were randomly separated into two groups: one group received positive instructions prior to a modified-caloric test and the other group received negative instructions. Participants then underwent a modified-caloric test with water set to 37 degrees Celsius and not expected to stimulate the vestibular system. Eye movements were recorded using the ICS Chartr 200 videonystagmography system. Physiologic variables included measurements of skin conductance and skin resistance using a GSR Shimmer unit. Subjective variables included a yes/no question about the presence of vertigo, a 7-point severity of nausea rating, and a 20-point motion sickness scale. Covariates included self-report State Trait Anxiety and Motion Sickness Susceptibility questionnaires. Average slow phase velocity of eye movements indicated no vestibular stimulation for either group. Self-reported perception of nausea and motion sickness were minimal and did not differ between groups. The negative instruction group yielded additional peaks in skin conductance and dips in skin resistance compared to the positive instruction group, suggesting increases in physiological arousal in the negative instruction group. Both groups presented with low State Trait Anxiety and Motion Sickness Susceptibility scores. Negative instructions prior to the caloric test did not produce subjective symptoms of nausea or dizziness. However, it does appear that negative instruction may contribute to higher levels of physiologic arousal during testing. Future research should consider allowing participants to first gain experience with caloric testing and sensations of vertigo prior to the experiment to better facilitate the formation of nocebo effects.

Recommended Citation

Weist, Abbey, "Induction of nocebo effects by verbal suggestions during the caloric test" (2020). Dissertations, 2020-current. 21.
https://commons.lib.jmu.edu/diss202029/21