Leiden University Scholarly Publications

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Meeuwis, S.H. (2020)

Placebo and nocebo effects in itch : from conditioning to psychophysiological effects

Doctoral Thesis
This dissertation investigated placebo and nocebo effects in itch. Placebo and nocebo effects are positive and negative treatment outcomes respectively, that cannot be attributed to active treatment ingredients. Consistent with previous research, the dissertation shows that these effects play an important role in itch. The studies moreover illustrate that placebo effects can still occur when people are informed about them.
The results described in this dissertation show that expectations about itch can be formed in various ways. People's expectations of treatment outcomes have been found underlie placebo and nocebo effects. For instance, the information that is given about how much itch an experimental test elicits (i.e., verbal suggestions) can influence expectations and lead to placebo or nocebo effects. The results also show that placebo effects can be automatically induced for itch by associative learning (through pharmacological conditioning). In...Show moreThis dissertation investigated placebo and nocebo effects in itch. Placebo and nocebo effects are positive and negative treatment outcomes respectively, that cannot be attributed to active treatment ingredients. Consistent with previous research, the dissertation shows that these effects play an important role in itch. The studies moreover illustrate that placebo effects can still occur when people are informed about them.
The results described in this dissertation show that expectations about itch can be formed in various ways. People's expectations of treatment outcomes have been found underlie placebo and nocebo effects. For instance, the information that is given about how much itch an experimental test elicits (i.e., verbal suggestions) can influence expectations and lead to placebo or nocebo effects. The results also show that placebo effects can be automatically induced for itch by associative learning (through pharmacological conditioning). In addition, these effects may also occur when people know they are placebo effects. These results illustrate the importance of expectations and the psychosocial context in the treatment of somatic symptoms complaints such as itch. The results of this thesis may help improve existing treatments for itch. For example, medicine use can potentially be reduced by applying pharmacological conditioning, existing treatment can be improved by providing optimal treatment information, and the importance of expectations for treatment outcomes can be discussed with patients.Show less
Placebo effects
Nocebo effects
Expectancy
Conditioning
Associative learning
Itch
Pruritus
All authors
Meeuwis, S.H.
Supervisor
Evers, A.W.M.
Co-supervisor
Middendorp, H. van; Veldhuijzen, D.S.
Committee
Brosschot, J.F.; Vermeer, M.H.; Peters, M.L.
Qualification
Doctor (dr.)
Awarding Institution
Institute of Psychology, Faculty of Social and Behavioural Sciences, Leiden University
Date
2020-06-03

Funding

Sponsorship
The research was funded by a Consolidator Grant from the European Research Council (ERC), granted to A.W.M. Evers.