You’ve heard of the placebo effect – but what’s the nocebo effect? Is pain all in the mind?

Researchers say the ability of ‘nocebo’ effects to spread to others may have implications for medical treatment such as group exercise for back pain. Photograph: PeopleImages/Getty Images

When Dr Henry Beecher had no morphine to offer wounded soldiers during the second world war, he started administering a plain saline solution to give soldiers at least the impression of receiving pain relief.

After the soldiers reported reduced pain, it was the beginning of Beecher’s studies into what he later called the placebo effect – a beneficial effect produced by a patient’s positive beliefs about a treatment. But what happens in the opposite scenario?

When a patient has negative expectations that a treatment will cause harm, and this belief leads to negative outcomes, this is known as the “nocebo” effect. A study published Monday in the journal Communications Psychology has found a nocebo effect has the capacity to spread, with evidence of individuals’ experience of pain heightened by witnessing other people’s responses to the same treatment.

Dr Kirsten Barnes, the lead author on the study who is from the School of Psychology at the University of New South Wales, said while less is known about placebo’s negative counterpart, the topic is receiving increasing interest.

Can a nocebo effect be transmitted?

In Barnes’ study of 101 participants, people were paired up and each person in the pair was given the role of either “demonstrator” or “observer”. The demonstrator was fitted with a small pulsating heat plate which they were led to believe would deliver an electrical current that would increase pain .

They were told that they would need to learn from one another when the treatment was switched on or off, based on the presence of a green or blue square presented on a computer screen in front of them.

In the first demonstration, the intensity of the heat was increased when the blue square was presented, but for all other demonstrators the same intensity of heat was applied irrespective of whether they saw the green or blue square.

“We found that as observers moved to the demonstrator’s position, they reported more pain to the blue square, even though there was no difference in the intensity of the heat,” Barnes said.

The results showed “they had learned about the negative effects of treatment from watching another person and then passed their own nocebo effect on to the next person who watched them. This change in pain was present in their pain ratings, but also in their facial expressions, and their physiological response,” she said.

Where have we seen other examples?

Historical examples have shown that watching other people experience symptoms such as pain can exacerbate those same symptoms in the observer, with mass psychogenic illness – where anxiety causes physical symptoms – first described over 600 years ago.

In November 1998, when a teacher at a Tenessee school smelt gasoline in her classroom and experienced a headache, nausea, shortness of breath, and dizziness, 100 teachers and students also ended up in the emergency department related to the supposedly toxic exposure – but no medical or environmental explanations for the reported illnesses were ever found.

A similar mass psychogenic illness occurred at a school in Ripon in the UK. More recently, Tourette-like symptoms were observed among young people in Germany after watching videos of similar behaviours on social media.

Dr Amelia Scott, a clinical psychologist and research fellow at Macquarie University, said “it’s very likely that nocebo effects are partly responsible for lots of public health scares, which can sometimes be amplified by alarming media reports or social media posts. For example, there’s evidence that shows large spikes in people reporting drug side effects after media reports raise the alarm.”

So is pain all in the mind?

Prof James McAuley, the director of Neuroscience Research Australia’s Centre for Pain Impact, is a back pain researcher and says he has seen evidence of both the placebo and nocebo effects.

“This research is so important because it shows that the pain somebody is experiencing isn’t always just to do what’s happening in their body,”he said.

“It’s not always associated with how much damage there might be wherever they can feel the pain. Your brain, and the processing that’s happening in your brain, plays a critical role in whether or not you experience pain, but also in the intensity of that experience.”

McAuley said the study clearly showed pain can be learned from other people, particularly other people that you feel close to, with a “social contagion of nocebo and possibly of placebo as well.”

So what should we take away?

Scott said the social transmission of nocebo effects make sense from an evolutionary standpoint. “It’s a very adaptive trait that promotes our survival if we can be closely attuned to each other’s experience of unpleasant symptoms, especially pain,” he said.

However, it can have negative implications in contemporary health settings. Barnes said there are many places where we might see other people having negative experiences of treatment – such as in shared hospital wards, in emergency departments, or when giving blood.

McAuley said the research also had implications for therapies in group settings – for example, exercises for back pain is often carried out in a group setting.