Universiteit Leiden

nl en

Lingling Weng aims to improve clinical practice with placebo and nocebo effects

The placebo effect was completely new to her when Lingling Weng began the PhD project in Leiden. She is now a postdoc in China. 'It would be great to investigate the underlying mechanisms of placebo and nocebo effects with my current knowledge of EEG and fMRI.' PhD defence on 17 October.

Placebo and nocebo effects

Placo effects refer to positive treatment outcomes, e.g., decreased pain due to positive expectations. Nocebo effects refer to negative treatment outcomes, e.g., increased pain due to negative expectations. 

Cover PhD Thesis Lingling Weng: Generalization of placebo and nocebo effects on somatosensory sensations

What did you discover as a new result for the research field?

'The results of my dissertation specifically showed that a pain sensation can be reduced (placebo effect) or increased (nocebo effect) by verbal suggestion and/or conditioning. Because of the previously learned effect on a pain experience, another type of pain sensation can also be affected. Also, an effect on an itch sensation after giving verbal suggestion may work on another type of itch sensation. Placebo and nocebo effects for one sensation seem to have little or no effect on another sensation, for example, from pain reduction to itch reduction.'

How did you find this result, using what research method?

'We tested healthy participants in a laboratory setting. To test whether the placebo and nocebo effects on one type of pain and itch sensation also apply to another type of sensation, we first induced placebo and nocebo effects on one sensation and then tested these effects on other sensations.'

'For example, we told participants that a liquid containing 'cyclosol' could increase itching and that a control liquid had no effect on itching caused by cowhage (derived from the tropical bean Mucuna pruriens). We then applied both liquids to participants followed by cowhage. After a short break, participants were again exposed to these two liquids, followed by a different kind of itching and touch stimulus, without any verbal suggestion.'

'Actually, these two liquids are just water and have no effect on itching. The results showed that cowhage itching was higher with the 'cyclosol' fluid than with the 'control' fluid. Thus, participants experienced nocebo effects on itching. The results also showed that itching caused by a different type of itch (but not that it was more itchy as a result of touch) was higher with the fluid containing 'cyclosol' than with the control fluid. Participants probably transferred their original experience to a different type of itch, but did not suddenly experience a touch as more itchy.'

Which part of your research project did you enjoy most?

'The placebo effect was completely new to me when I started the PhD project. The learning itself gives me a lot of pleasure; learning how to use equipment to induce heat pain, pressure pain, itching and touch, learning how to create conditioning and verbal suggestions, learning how to perform the experiments in the laboratory; all fun experiences.'

'Lately I've been enjoying writing. I enjoy sitting down, thinking, writing down my thoughts and explanations of the results, and revising my work. Writing is a way to mentally revisit the whole experiment rather than physically testing.'

What are you doing with your knowledge now?

'I am working as a postdoc at a Chinese university and also doing placebo and nocebo research. Since I have little experience with neuroscience, such as EEG and fMRI studies, the current research group offers me a great opportunity to learn these neuroimaging skills. It would be great to investigate the underlying mechanisms of placebo and nocebo effects. And with my knowledge, I would like to focus on translational research to improve treatments in clinical practice in the future.'

This website uses cookies.  More information.