Thesis defense Karolina Świder (Donders series 356)

5 February 2019

Promotor: prof. dr. J. van Luijtelaar
Co-promotors: dr. hab. P. Bąbel, dr. C. van Rijn, dr. J. Oosterman

Pain perception – power of placebo effect and crossed-hands analgesia

The most known and studied psychological influence on pain perception is the placebo effect, that may produce pain reduction (placebo analgesia) or pain worsening (nocebo hyperalgesia). Additionally, pain can be reduced by crossing hands over the body midline (crossed-hands analgesia) and focusing attention away from a nociceptive stimulus. This dissertation presents five studies on factors influencing the magnitude of placebo effect induced by social learning, hidden/open conditioning, verbal suggestion and one study on crossed-hands analgesia in the context of attention manipulation. The results presented in Chapter 2-5 indicate the role of factors such as the sex of the model, empathy, fear as a trait and state, and anxiety as a trait and state on the placebo effect. In Chapter 2, the sex of the model was shown to influence the magnitude of nocebo hyperalgesia induced by social learning. The type of stimuli used as placebos described in Chapter 3 exhibited no influence on the placebo effect induced by social learning. It was shown that placebo analgesia and nocebo hyperalgesia can be induced by hidden conditioning (Chapter 5). Placebo analgesia induced by hidden conditioning was shown to be predicted by self-reported fear (Chapter 5). Finally, the results from Chapter 6 point to a strong influence of attention manipulations on the pain ratings and on the brain activity, suggesting that hand position may modulate the strength of attentional effect. In conclusion, the results extend the knowledge about the influence of cognition on pain perception. The results may supplement Colloca's and Miller’s model of placebo induction and also indicate the influence of attention on pain perception.