Medical Trust Networks

When it comes to health, the online debate can be very intense, involving a range of actors, from government and science institutions to citizens voicing opinions in (organized) patient forums, blogs, and tweets. Actors may refer to highly discrepant information sources, and opinions show strong dynamics. In the Netherlands, online debates recently focused on the human papilloma virus (HPV) and the Swine flu virus vaccination programs. Both led to strong negative opinions about the programs and against vaccinations in general, despite best efforts of the RIVM to provide the public with neutral and evidence-based counterarguments. As a result, the HPV vaccination campaign was only partially effective (56% of the target group in 2012, 58.1% in 2013 and 60% in 2014).

What became clear from these debates is that within different communities, different belief systems exist. Interconnected social networks with shared belief systems can be seen as trust networks. Because protecting belief systems is key to the viability of such trust networks, members apply diverse defensive strategies when belief systems are challenged, such as opinion disconfirmation and discounting, or actor exclusion, derogation, and ostracizing. As a result, outside influence on opinions in trust networks is very limited – within-group processes yield convergence of opinions and narrow latitudes of acceptance.

This project will make a first investigation to detect belief system dynamics in online trust networks, aiming to study how beliefs converge, collide, and are countered, and how (dis)trust develops within and between trust networks over time. We use two existing data sets from RIVM that were manually annotated with meta-data, topic and sentiment.5 The first was collected from online message boards where people discuss the use of medicine in relation to diabetes, ALS and ADHD, the second from social media and news on the measles outbreak in 2013.

For a further description of the project, please visit