Universiteit Leiden

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PhD defence

Harnessing placebo effects by targeting expectancies

Wednesday 7 February 2018
Academy Building
Rapenburg 73
2311 GJ Leiden

Short summary

Placebo effects are health improvements, for example pain reduction, due to an inert treatment. These effects are typically ascribed to a person’s expectations about the beneficial outcomes of the placebo. 
The literature and experimental research in the current dissertation shows that expectancies, and thereby placebo effects, can be induced via verbal suggestion, conditioning, and mental imagery. Especially verbal suggestions may enhance analgesic treatments for patients. We found, for the first time, that mental imagery of reduced pain can induce analgesia via its effects on pain expectancies. We also observed that people’s expectations about the effectiveness of medications depend on the route of administration and targeted symptom. 
These findings suggest that harnessing placebo effects by targeting expectancies is promising for enhancing standard clinical care of physical symptoms.


  • Prof. A.W.M. Evers
  • Prof. M.L. Peters


PhD defences are free; you do not have to register.

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

Maarten Muns, Scientific Communications Adviser, Leiden University
+31 71 527 3282

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