Default Mode Network Connectivity and Nocebo Responses in Migraine: A Functional MRI Study

People with migraine sometimes experience symptoms because they expect a treatment to cause side effects. This is known as the "nocebo effect". Unlike a drug side effect, a nocebo effect is triggered by negative expectations rather than by the treatment itself. Nocebo effects can reduce patients' confidence in treatment and may lead them to stop taking medications that could help control their migraine. Understanding why some people are more likely to experience nocebo effects could help healthcare professionals improve treatment discussions and support long-term treatment adherence.

The aim of this study was to investigate whether changes in brain activity are associated with nocebo responses in people with migraine. Researchers focused on the "default mode network" (DMN), a group of interconnected brain regions involved in self-reflection, emotions, memory, and expectations. Because expectations play an important role in nocebo effects, the researchers examined whether communication within this brain network changed during a nocebo challenge.

Forty adults with migraine were recruited from the Headache Clinic of Aeginition Hospital, National and Kapodistrian University of Athens, between October 2019 and February 2023. All participants underwent magnetic resonance imaging (MRI) and resting-state functional MRI (rs-fMRI), a technique that measures communication between brain regions while a person is resting. Participants were then randomly assigned to one of three groups. One group received an intravenous saline infusion together with the suggestion that they might experience numbness. A second group received only the same verbal suggestion, without the saline infusion. A third group received no intervention. Thirty minutes later, participants reported whether they had experienced numbness before undergoing a second brain scan. Participants also completed a questionnaire measuring their susceptibility to nocebo effects. Four participants were excluded because excessive movement affected the quality of their MRI scans, leaving 36 participants for the final analysis.

This study investigated whether changes in DMN connectivity were associated with the nocebo challenge and whether these changes differed between participants who did and did not report numbness. By identifying brain mechanisms involved in nocebo responses, this research may improve our understanding of why some people are more susceptible than others. Although the study was exploratory and included a relatively small number of participants, its findings may contribute to future strategies that help clinicians identify patients at greater risk of nocebo responses, communicate more effectively about treatment, and improve adherence to migraine therapies. Larger studies are needed to confirm these findings before they can be applied in routine clinical practice.