A few weeks ago, we discussed the surprising power of the placebo effect. 

You may recall that pills with no known beneficial effect can work miracles to relieve symptoms, especially pain, provided patients are convinced of the effectiveness of the pills.

The effect is well-described and, in some instances, has been shown to work because suggestion can release naturally occurring opioids in the brainstem.

But if the release of the opioids is blocked by naloxone, so also is the placebo effect.

That was convincing evidence for a biological explanation for at least some placebo effects. 

But you might not be so familiar with the nocebo effect, which suggests that beliefs can make us sick. 

The nocebo effect refers to the occurrence of harmful effects from consciously or unconsciously anticipating symptoms, one example of which was the June bug incident of 1962.

Employees at a United States dress manufacturing plant developed symptoms such as faintness, nausea, abdominal pain, headache and fatigue, for which no toxin in the water or air, or infectious agent, were found to explain the mass illness. 

Then, there’s the example of the Havana syndrome reported in U.S. embassies around the world, in which employees reported similar symptoms, as well as difficulties concentrating and focusing — what would now be called brain fog. 

Yet, despite claims that adversaries were subjecting employees at embassies and some military installations that some form of high-tech sound waves or electromagnetic radiation were the cause of the symptoms, no evidence was later found to substantiate those claims.

Recently, a five-year study by the National Institutes of Health, reported in the Journal of the American Medical Association, found no evidence of injuries to the brain volume, structure and white matter and no significant differences in cognitive function between those reporting the symptoms and healthy subjects.  

Similar mass events have been described in schoolchildren at the same school and usually of like age, although the symptoms often spread to younger children in the same school.

These few examples speak to the many examples of dramatic mass illnesses with similar symptoms, for which no obvious plausible medical cause could be found.

But if no medical and scientific plausible causes have been found for the foregoing examples, what explains the phenomenon?

Some experts suggest that the symptoms are entirely functional — that is, they’re all in the patients’ heads and fabricated in some fashion.

Possibly, but much more likely, is the probability that the symptoms are physically real, even if not caused by an identifiable agent.

After all, fear and anxiety are contagious, as are their accompanying symptoms and behaviours. 

Similar group symptoms have been reported in high-stress situations such as mass shootings, and civilians and troops under continuous bombardment.

Lack of sleep and inability to get away are common these days in Ukraine and Gaza, where stress-related symptoms are very common.

Why would we be surprised?  

That doesn’t explain the spread of like symptoms to other members in a group, except that in primates such as chimpanzees, some members of a troop will literally “ape” or copy symptoms and behaviours of others in the troop.

Such mirrored behaviour may be explained by the observation that some neurons in the brains of observers, sometimes “mirror” the firing patterns of neurons in those primates carrying out specific tasks — we are neurally wired to literally “ape” the behaviour and presumably feelings of others in groups.    

Recently the Mayo Clinic released a book on the subject, written by Michael Bernstein, Charlotte Blease, Cosima Locher and Walter A. Brown (no relation) titled, “The Nocebo Effect: When Words Can Make You Sick.” 

It’s worth a read and a reminder, if readers need reminding, that the Mayo Clinic is one of the best medical facilities in the world, where the quality of the staff is uniformly high, well-coordinated, and their approach to patients is very user-friendly, to which almost anyone who has gone there for care can usually attest.

I know several of their staff, many of whom are now retired and one of their past CEOs — all are terrific examples of the clinic’s high standards. 

This may sound like a plug for the Mayo Clinic, and it is for the very sound reasons I’ve mentioned, and the high quality of care they provided to patients I referred to Mayo from northern Ontario when I was a visiting physician in Thunder Bay’s multiple sclerosis and general neurology clinics.

They were always a great help even if they, like the rest of the profession, didn’t always have the answer.

Dr. William Brown is a professor of neurology at McMaster University and co-founder of the InfoHealth series at the Niagara-on-the-Lake Public Library.