The Mind's Power to Heal and Harm

 For the past few years, I've been writing a book, This Book May Cause Side Effects, about how our thoughts influence ill health. You may have heard of the placebo effect, when positive expectations lead to positive health outcomes. But my interest is in its evil twin. The nocebo effect occurs when dismal expectations lead to negative health outcomes. The phenomenon can create, exacerbate and prolong symptoms. When these symptoms coalesce, people become ill - not from disease, but from the intimate relationship that exists between mind and body. Sometimes, all it takes to make someone feel genuinely unwell is a few carefully chosen words.

 

The Doctor
Luke Fildes (1843-1927)
Photo Credit:Tate Britain [CC BY-NC-ND] 

You don't just have to take my word for it. There is a plethora of peer-reviewed studies confirming this idea. In one, patients fresh from minor keyhole surgery received a harmless saline infusion that they were told would temporarily increase their pain. It did just that. In another, 40 asthmatic adults breathed in water vapour from an inhaler they were told contained an irritant. Nineteen went on to feel wheezy. Twelve had a full-blown asthma attack.

These are artificial situations, but the nocebo effect is out there in the real world too. If you've felt lousy after having the Covid-19 vaccine, there's a good chance your symptoms weren't caused by the vaccine. Combining data from 12 separate clinical trials involving more than 45,000 participants, scientists found that large numbers of people who got placebo shots had adverse side-effects, leading them to conclude that the nocebo effect accounted for a huge 76% of all common adverse reactions to the jab...

During the pandemic, the nocebo effect was responsible for an outbreak of tics that was propagated when young people saw videos of them on TikTok. It became known, fittingly, as the TikTok tics. Now, researchers believe we live in an era in which, increasingly, social media are turbocharging the spread of nocebo-generated symptoms...

I believe that if we want to be well, it's important first to understand the many ways that we become ill. The nocebo effect - underestimated and overlooked - is a key part of this puzzle.

(Helen Pilcher, The Guardian, 2026)

Why is it not the case, with both the placebo and the nocebo effect, that all the participants felt better or worse? What are the factors that influence people's thoughts regarding the benefits or negative effects of medical treatment? Why are some people more receptive to what the effects will be? Is there any alignment between these medical effects and those that are promulgated by the influencers on social media?