Prof. Ben Colagiuri - Professor and Head of the Department of Psychology at the University of Sydney/Australia
If you’re sufficiently afraid of certain symptoms, you might actually develop them, especially if they’re unspecific symptoms that are part of lots of illnesses, like headaches or generally feeling unwell. And if you read on the internet that lots of patients are reporting a particular side effect of a medication you’re taking, you might start to expect this side effect and then feel it yourself, even if you hadn’t previously noticed it. This is how, through an intensive preoccupation with health information in the digital world, the nocebo effect can impede the recovery process and even promote illness.
COVID-19 is a fascinating and especially prominent example of how nocebo effects can spread through social media. It is known that COVID-19 vaccinations can have adverse effects. But it also turns out that if people are exposed to negative reports about vaccine side effects before getting their vaccination, be it on social media or through their personal social contacts, they are more likely to report side effects after their own vaccination, and will also perceive them to be stronger.
Ben Colagiuri is an international expert on the role of expectations and placebo and nocebo effects. He examines, for example, how warnings about potential side effects can influence the frequency and severity of the side effects that actually occur. According to Colagiuri, “In a study, if we give one group a placebo treatment for sleep disorders, and mention warnings about side effects, then this group will report more side effects than a group that is just given the placebo without any warnings.”
Together with researchers from Australia, the USA, Great Britain, and Denmark, in two studies, Colagiuri examined the relationship between posts on social media such as Twitter/X and side effects following COVID-19 vaccinations.
- First of all, the researchers asked 280 people in Australia to tell them retrospectively about side effects after their COVID-19 vaccination. The result: The more negative personal posts about vaccination side effects the participants had read on various social media platforms before getting vaccinated, the more severe they reported their own post-vaccination side effects to be. And this relationship was even stronger in participants who rated themselves as more anxious, depressive, and stressed. Moreover, the effect was also stronger if the posts were on an online social community that the respondents felt close to. The factor of whether respondents generally trusted social networks more than, for instance, official government statements also played a role: Whomever respondents trusted the most had a greater influence on their expectations and also on the severity of adverse effects.
- In a so-called prospective study (i.e. one that follows people over time), 551 participants were asked about their media consumption (news reports compared to social media posts) before their COVID-19 vaccination and about first-hand accounts from personal acquaintances. After getting their vaccination, they then reported on side effects like tiredness, fever, or aching limbs. The results showed that the number of negative posts viewed on social media, and the amount of negative information gleaned from friends and family, initially increased respondents’ negative expectations regarding vaccine side effects. Furthermore, after getting their vaccination, it emerged that participants who had received negative information in advance also experienced stronger and more frequent side effects. Colagiuri explains that “this gives us reason to believe that what we hear and see from others on social networks has the power to influence our own reactions – via nocebo effects”.
Elon Musk’s post with millions of hits
A striking example of just how far-reaching a social media post can be was provided by Elon Musk. Thanks to Tesla, SpaceX, Twitter/X and many other technology companies, Musk is one of the richest, most well-known, but also most controversial people in the world. On February 21st, 2021, Musk posted on Twitter that: “I had major side effects from my second booster shot. Felt like I was dying for several days. Hopefully, no permanent damage, but I dunno.”
20 million users saw this Tweet, and 155,000 “liked” it. In total, Elon Musk has 209.5 million followers (as of March 2025).