Negative expectations of treatment increase the chance of pain

Dossier Research in the spotlight
Dossier Research in the spotlight

Many people experience more pain if they have negative expectations of treatment. What happens here in our brain? PhD candidate Mia Thomaidou conducted research into this nocebo effect. She discovered how brains convert negative expectations into pain signals. PhD defence on September 7.

It is always good to read the medicine information leaflet, but focusing too much on possible negative effects is not advisable, says neuropsychologist Mia Thomaidou. She investigated the brain mechanisms involved when negative experiences or expectations about pain cause people to experience the pain as worse - just as positive expectations can lead to the placebo effect. ’Our brains try to predict what will happen next and involve memories and emotions in that process. They pass on pain sensations if these emotions and memories are negative.’

Study with participants

Thomaidou’s study, which is part of a large-scale study of the nocebo effect, shows that the brain can quickly be led astray. She conducted a number of experiments with around 400 healthy participants. In one experiment, the participants were told that a cream (which was actually a harmless moisturiser) would make them feel more pain in a specific spot on their arm. When a low-heat pain was administered to their skin, the majority of the participants reported feeling more pain in this spot.

Brain research

The research team tested the participants’ physiological responses by measuring their muscle responses and activation of certain brain areas with an fMRI scan. Thomaidou says, ’When people expect more pain, we tend to see increased activity in the areas - such as the frontal lobe, insula and amygdala - that evaluate incoming pain signals based on prior experiences and expectations.’

Take account of nocebo effect

It is important to take better account of this nocebo phenomenon, Thomaidou stresses. She gives the example of research on new drugs in which all participants are informed about possible negative side effects. Many studies show that even the participants in the control groups who do not receive the medication tend to report these negative side effects having received this information. ’My study also illustrates how expectations influence our future experiences. This makes it important for doctors to be careful not to overemphasise possible painful effects when treating pain or illness.’

This study is part of health psychologist Andrea Evers’ research on the impact of expectations on health through placebo and nocebo effects, for which she has received a European Consolidator Grant.

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Academic staff

PhD Defence How negative experiences influence the brain in pain: Neuroimaging and biobehavioral insights Mia Thoma´dou

European City of Science Leiden 2022 De dag van het placebo-effect Andrea Evers