The intriguing link between sensitivity to physical and psychological pain

Everybody hurts? Not Jo Cameron, who often needs to be told if she is bleeding or bruised

Jo Cameron, who has a rare disorder that means she does not experience pain or anxiety, in Gilsland, England. Photograph: Mary Turner/The New York Times

Jo Cameron, who has a rare disorder that means she does not experience pain or anxiety, in Gilsland, England. Photograph: Mary Turner/The New York Times

 

A recent article about Jo Cameron – who has lived for 71 years without experiencing pain or anxiety because she has a rare genetic mutation – prompted many questions.

The notion that the same gene could be responsible for the way a person processes physical and psychological pain left many perplexed: aren’t they totally different? Or does her story hint that sensitivity to one type of pain might be intertwined with sensitivity to another?

Childbirth, Cameron said, felt like “a tickle”. She often relies on her husband to alert her when she is bleeding, bruised or burned because nothing hurts.

When someone close to her has died, she said, she has felt sad but “I don’t go to pieces”. She cannot recall ever having been riled by anything – even a recent car crash. On an anxiety disorder questionnaire, she scored zero out of 21. “I drive people mad by being cheerful,” she said.

Here’s a bit about what’s known:

Do those who live without pain also live without anxiety?

No. Before encountering Cameron, the scientists who studied her case worked with other patients who did not experience pain. “Reduced anxiety has not really been noted before in the other pain insensitivity disorders we work on,” says Dr James Cox, a senior lecturer from the Molecular Nociception Group at University College London.

He also said that given Cameron had gone more than six decades without realising just how unusual she was, there could be others like her.

A number of such individuals contacted the New York Times after the article was published. “I also had the children and no pain,” wrote Juanita Hoffman (81) of Dayton, Ohio. “I thought family and friends who complained were just drama queens.” Asked about her mental state, she wrote: “No, I have never experienced anxiety. I have always been content and happy.”

How could a genetic mutation wipe out anxiety?

Cox believes Cameron’s reduced anxiety was “related to increased signalling at CB1 receptors”, or cannabinoid receptors, which are known to help the body deal with stressful situations. (Notably, they are activated by the THC in cannabis.) Block the cannabinoid receptors and anxiety will increase; boost the cannabinoid receptors and anxiety will fall, studies have shown. The receptors also affect how people experience physical pain.

Does that mean physical and mental pain are processed the same way?

No, it’s more complicated than that, and lots of research is still needed, says Dr TH Eric Bui of the Center for Anxiety and Traumatic Stress Disorders and Complicated Grief Programme at Massachusetts General Hospital. What we do know, he said, is that “brain regions that process emotional and physical pain overlap”. In another example of how mysteriously intertwined the two types of pain can be, he noted that paracetamol had been shown to decrease the emotional pain that comes with rejection.

So is rejection similar to physical pain?

Naomi Eisenberger, a professor in the University of California, Los Angeles, psychology department, believes so. Eisenberger studies the similarities in the way that the brain processes physical pain and the “social pain” that results from rejection. She said she had repeatedly found that “people who are more sensitive to physical pain are more upset by rejection”.

Do low-anxiety people seem to feel less pain?

In general, yes, according to some pain-management experts. Adam Woo, a consultant in pain and anaesthesia at King’s College Hospital in London, has worked with thousands of patients dealing with pain. Patients with high levels of anxiety tend to be more sensitive to pain, he has found. “If you have anxiety, it makes your perception of pain worse,” he said. And if two patients are facing the exact same kind of injury, the one with more anxiety tends to have a “higher complaint score”, he says.

Why do anxious people seem to have a lower pain threshold?

Debra Kissen, executive director of Light on Anxiety, a treatment centre in Chicago, believes that some people truly are just more sensitive – as in they seem to feel more intensely. That said, she has observed the way that anxiety and physical pain can amplify each other. Afflicted with chronic pain, a person may start to feel anxious that they have no control over their body. Then their anxiety may increase their focus on the pain, exacerbating it. Treat either one and it will sometimes help both, she said. What she finds most intriguing about the two kinds of pain is the consistency in her patients’ answers to a choice. “I’ll ask someone, ‘You can either stub your toe and it hurts an eight [out of 10], or feel emotional despair,’ ” she said. Patients always pick the toe. – New York Times

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