Placebo and nocebo effects on itch: An experimental approach

Bartels, D.J.P. (2020)

Doctoral Thesis

Placebo and nocebo effects are positive or negative treatment effects respectively, unrelated to the treatment mechanism, which are induced by patients’ expectations. Placebo and nocebo effects are known to play a role in treatment effects for various symptoms and conditions, especially in the field of pain. The aim of the current disseration was to increase understanding of placebo and nocebo effects on itch.
The results of the studies presented in this thesis further underline that placebo and nocebo effects play a role in itch perception. We found that itch is highly susceptible to suggestions and placebo and nocebo effects can be induced on itch by verbal suggestion and conditioning. Most notably, our findings show for the first time that particularly the combination of conditioning with verbal suggestion is most promising for inducing both placebo and nocebo effects on itch, which is in accordance with placebo research on pain. Moreover, a new and promising finding is that counterconditioning has shown to reverse nocebo effects on itch. Future research may build upon the findings of this thesis to further enlarge our knowledge on placebo and nocebo effects on itch and how to maximize or minimize them, respectively, also in a clinical setting, to eventually optimize available interventions for patients suffering from chronic itch.

• Placebo
• Nocebo
• Itch
• Scratching
• Conditioning
• Verbal suggestion
• Counterconditioning

• All authors: Bartels, D.J.P.
• Supervisor: Evers, A.W.M.; Kerkhof, P.C.M. van de
• Co-supervisor: Laarhoven, A.I.M. van
• Committee: Does, A.J.W. van der; Jong, E.M.G.J. de; Dijkerman, H.C.
• Qualification: Doctor (dr.)
• Awarding Institution: Institute of Psychology, Faculty of Social and Behavioural Sciences, Leiden University
• Date: 2020-11-18