From headaches to tics, how mass nocebo effects spread real symptoms

Centuries ago, witches and shamans would mutter curses with the intention of spreading illness. Today, certain social media feeds may serve the same purpose.

We aren’t talking about sharing dubious claims about quack treatments and fad diets, but rather information that exaggerates threats to our health. Through the power of suggestion, these posts can trigger real symptoms – ranging from Tourette’s-like tics to headaches, muscle pain, fainting fits and even cognitive impairment.

That negative expectations can influence our health is already well established – it is called the “nocebo effect” and there is increasing interest in how it can pass from person to person. Scientists have shown that the phenomenon can be highly transmissible, spreading through face-to-face conversations, blogs and – most worryingly – social media.

“Online information can spread nocebo effects faster and farther than has previously been possible,” says Kate Faasse at the University of New South Wales in Sydney, Australia. “This is quite scary, given how many people seek health information on the internet and through social media in particular.”

Contagious nocebo responses are so common that you may have experienced one yourself – ever witnessed someone vomit and then felt nauseous? Fortunately, recent research is offering new ways to protect ourselves from these mind viruses.

The placebo effect’s opposite

Even if you have never heard of the nocebo response, you will probably be familiar with its counterpart – the placebo effect. In many situations, this can lead to people feeling better as a result of the mere expectation of relief. Taking a sham pill presented as…