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PhD defence

Optimizing placebo effects in medical contexts: Utilizing learning theories and exploring communication strategies

Tuesday 14 September 2021
Academy Building
Rapenburg 73
2311 GJ Leiden

Short summary

This dissertation covered several relevant cycles of placebo research with the main aim to optimize placebo effects in medical contexts.

Firstly, a literature review described how the immune system can be impacted by placebo effects and their underlying learning theories. In the following chapter, these learning theories were integrated to form an optimal research design by means of pharmacological conditioning to fit a specific patient group: children with juvenile idiopathic arthritis.

Secondly, this dissertation focused on developing placebo information strategies to harness placebo beliefs and educate persons about the relevancy of placebo effects in practice. These insights are valuable because treatment expectations can have a positive or negative effect on treatment outcomes.

Finally, insights from placebo learning theories and placebo information strategies were combined in an integrative experimental research design. This research design employed a more ethical form of placebo effects because participants were made aware of placebos, called open-label placebos. In this last study we demonstrated that open-label placebo analgesia can be induced by combining learning theories and placebo information strategies.

Altogether, this dissertation provided insights in learning mechanisms, communication strategies, and research paradigms that involve the optimization of placebo effects in medical context.


  • Prof. A.W.M. Evers
  • Prof. N.M. Wulffraat

PhD dissertations

PhD dissertations by Leiden PhD students are available digitally after the defence through the Leiden Repository, that offers free access to these PhD dissertations. Please note that in some cases a dissertation may be under embargo temporarily and access to its full-text version will only be granted later.

Press contact (only for journalists) 

communicatie@leidenuniv.nl (+31 71 527 4690)

Practical questions:

Pedel's office (+31 71 572 7211)

Dissertation Rosanne Smits summary.pdf

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