22-05-2025
Rumours on social media could cause sick people to feel worse
THE PLACEBO effect is a well-known example of the brain's power over the body, allowing people who are poorly or in pain to improve if they are led to believe they are being treated. The opposite, however, is also possible: patients who believe that procedures will cause them to suffer ill effects can make themselves worse.
The roots of this anti-placebo, or nocebo, effect are difficult to untangle. But in a paper in Health Psychology Review, researchers in Australia have pooled the available evidence and ranked the contributing factors. Misinformation on social media seems to come near the top. In fact, what psychologists call social learning—the drawing of inferences from the views of others—was found to be as powerful as lived experience, and more influential than information given by a doctor.
This is a problem, says Cosette Saunders, a psychologist at the University of Sydney and lead author of the study. Social learning may not be able to spread infection or cause new disease, but it can drive harmful side-effects. And managing these side-effects costs health systems around the world billions of dollars.
Take cancer treatment. In recent years, new drugs have emerged to control the side-effects experienced by people receiving chemotherapy. But Dr Saunders says that vomiting and nausea have not come down in cancer patients by as much as expected. Social learning may be responsible. 'They'll say, their mother-in-law had chemo twenty years ago and she was vomiting every single day," Dr Saunders says. 'Those kinds of long-held beliefs are influencing them now, even though the medical landscape has changed."
Something similar appeared to be happening during the covid-19 pandemic: studies in America and Australia found people who were most exposed to the idea that vaccination provoked side-effects were also most likely to report them.
Though the impact of the placebo effect has been recognised for centuries, work on the nocebo effect is much newer. Only in the past two decades have many scientists been convinced of its real-world impact, helped by studies that demonstrate how a negative attitude can lead to physical symptoms such as increased heart rate and physiological arousal.
The conclusions of the Australian analysis are stark about the power of social learning. But, says Dr Saunders, it is hard to know how much of these effects are down to social-media use as opposed to, say, chatting with friends at the pub. Dr Saunders' lab is one of many now trying to find ways to minimise the damage. One possibility is to balance warnings of nasty side-effects with positive testimony from patients who had no problems. If she finds something that works, she'll pass it on.
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