Woman who feels no pain: U of C researcher studies Scottish granny's unique DNA

A University of Calgary scientist is sharing what he and his fellow researchers learned when looking at the curious case of a woman who feels no pain. 

Matthew Hill is a neuroscientist with the Hotchkiss Brain Institute at the University of Calgary. He is one of several researchers who recently published a study in the British Journal of Anaesthesia about the woman's unique DNA.

A few years ago, Hill said, doctors in Scotland became fascinated with the woman, now 71 years old, after she underwent surgery for her arthritis.

After something that normally required a fair amount of post-operation analgesia, Jo Cameron seemed totally fine without it. 

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According to Hill, one of the doctors followed up with her and started asking questions. They realized that this was a history she'd had throughout most of her adult life.

"And as far as she could remember, she'd never really used painkillers for things," he told the Calgary Eyeopener. 

Reported childbirth as 'pleasant' 

"She had a lot of scars across her her hands, had undergone things like hip replacement surgery and always reported childbirth as being just fine, pleasant or not painful at all."

And, Hill said, this was more than just a case of a high pain tolerance. 

"It seems, in many ways, more like an insensitivity to pain," he said.

"She just didn't seem to be able to perceive that something was kind of a painful stimulus the way the rest of us would have."

That could be potentially dangerous, since pain is meant to warn people when something bad is happening to their bodies. 

Burns with no pain

"A good example of it is her description of some events that she didn't realise she'd had," he said. 

"She burned her hand on a hot burner until she smelled the smell of her burning skin, or she didn't realize her arthritis had progressed to the point where, basically, her legs gave out because they weren't working."

But, according to Hill, researchers found that in addition to her lack of physical pain experience, Cameron was also not experiencing pain to the same degree as other people psychologically.

"They started asking her about if she ever felt anxiety or fear in response to things and she described things that many of us would find traumatic — like car accidents — that she described as not producing any sense of anxiety or fear either," he said. 

"She seemed to also [have] blunted stress response or reduced emotional behaviour."

Chili pepper test

In order to test the woman's pain tolerance, Hill said, researchers did various tests including one at Hill's request, where they looked to see whether she was able to eat a lot of chili peppers. 

Hill said he asked for this test to be conducted because it looked as if Cameron was resistant to the actions of a substance inside chili peppers called capsaicin, which gives them their hot taste.

"She took a scotch bonnet pepper in the lab and ate it whole and reported a pleasant tingle in her mouth and the mind, which is not the way I think the rest of us would normally describe a scotch bonnet," he said.

When taking a closer look at what caused the woman to feel no pain, scientists found two notable genetic differences in her DNA, both of which impact a gene that regulates the body's endocannabinoids, something Hill describes as "the brain's version of THC" — his area of expertise.  

"So she had really high levels of endocannabinoids, and we we think that that actually may have conferred this kind of pain insensitivity as well as her blunted emotional responses to fear-inducing stimuli."

Potential as 'novel approach in pain medication'

Hill said the researchers' findings could prove to be helpful for others. 

"The thought is that the system that she has that's kind of dysregulated might be targetable for other people as a novel approach in pain medication," he said. 

In fact, Hill said, a drug has been made that blocks the enzyme in question — but it doesn't seem to have worked properly. 

"There's some thought that might reduce pain, but for some reason in healthy adults just giving them a drug to block this enzyme doesn't seem to fully reproduce her phenotype," he said. 

"So we're not exactly sure why that is. It might require longer term treatment. I mean, she's had these gene changes her whole life."

With files from the Calgary Eyeopener