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Chronic pain: the long road to discoveryChronic pain: the long road to discovery
The science is building and viable treatments are available.
But millions of people with chronic pain are still without help.
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Philip Kass spends 90% of his day lying on a twin bed in a sparsely decorated room that used to belong to his niece. He takes most meals with a plate balanced on his chest, and he usually watches television because reading is too stressful.
“I’m barely living,” he told me on a warm night in June last year.
Ever since a back injury 23 years ago, pain has been eating away at Kass’s life. It has cost him his career, his relationships, his mobility and his independence.
Now 55, Kass lives with his sister and her family in San Francisco, California. He occasionally joins them for dinner, which means he’ll eat while standing. And once a day he tries to walk four or five blocks around the neighbourhood. But he worries that any activity, walking too briskly or sitting upright for more than a few minutes, will trigger a fresh round of torment that can take days or weeks to subside.
“It’s just paralysed me,” he says.
Philip Kass has dealt with pain for more than two decades.
Some of what Kass describes is familiar. I have been pinned to the floor by spinal pain several times in my life. In my twenties, I was immobilized for three months. In my thirties and forties, each episode of severe pain lasted more than a year. I spent at least another half decade standing or pacing through meetings, meals and movies — for fear that even a few minutes spent sitting would result in weeks of disabling pain. For years, I read anything I could find to better understand why my pain persisted.
The picture that emerged was complex and surprising. Over the past few decades, a growing body of evidence has indicated that the very machinery that processes pain can help to sustain the sensation or make it worse. Some researchers have explored unexpected interactions between the immune and nervous systems, showing, for instance, that inflammation, long considered a provocateur of pain, might also be crucial for resolving it. Others have shown how depression, anxiety and other kinds of emotional distress can both feed — and feed off — the experience of pain.
Although there are treatments that acknowledge this multifaceted, biopsychosocial nature of pain, medical practice hasn’t kept pace with the science — not by a long shot.
Around the world, physicians are prescribing the same kinds of intervention for chronic pain conditions that they have offered for decades. Many people aren’t getting treatment at all. And in North America and Australia, opioid overprescription and misuse have resulted in tight restrictions on one of the main tools long used by clinicians for managing pain. Kass, and the half-dozen other people I interviewed who live with pain, have spent years bouncing from doctor to doctor, trying to find someone who can eradicate their torment, or at least lessen it. And they’re not alone.
In the last major survey, conducted in 2016, around 20% of adults in the United States — about 50 million people — had experienced pain on most days or every day in the previous 6 months. Around 8% — nearly 20 million people — had high-impact chronic pain, the kind that interferes with work or day-to-day activities1. Similar numbers have been reported from surveys conducted in Europe.
Although the pain research field is small, and fractured between different specialities, some researchers and clinicians argue that the knowledge and tools are already available to treat people with chronic pain conditions more efficiently and effectively than has been done in the past. What’s needed, they say, is the will to get there — from both the medical establishment and society at large.
“We have a lot of treatments and approaches that already can make an impact, but we need to get them into people’s hands, and we need to pay for it,” says Sean Mackey, a physician-scientist at Stanford University in California.
Pain often seems like a simple experience: grab a hot pan, and a harm alarm will sound. But in many cases where pain persists, the relationship between pain and harm is anything but simple.
In 1996, when Kass was 28, he was working as an acrobatics instructor with a travel and tourism company in the Bahamas. One morning, after a day of catching people on the flying trapeze, he was awoken by excruciating pain in his lower back.
He quit his job and flew back to the United States, where magnetic resonance imaging (MRI) revealed damage to a cartilaginous disc in his lower back, between his L5 and S1 vertebrae.
It’s impossible to know exactly what was going on in Kass’s body in the first hours and days after his injury. The specialists he saw in the United States told him that fragments of material from the damaged disc were probably pressing on his spinal nerves. But assuming Kass had experienced some kind of tissue damage, inflammation resulting from that would almost certainly have altered his pain-processing machinery.
Researchers have known for decades that tissue damage can alter the sensitivity of neurons in the peripheral nervous system (all of the nerves that exist outside the spinal cord, brainstem and brain), as well as how the central nervous system interprets signals.
After a sunburn, for instance, warm water that felt pleasant the day before might seem scalding. This happens because the inflammation caused by the sunburn alters the sensitivity of nerves in the peripheral nervous system known as nociceptors, which recognize noxious stimuli — a phenomenon called peripheral sensitization. Similarly, days after surgery, well away from the site of the incision where there is no inflammation, a light touch of the skin might hurt. That’s thanks to changes in the central nervous system. Multiple mechanisms drive this process, known as central sensitization, but in this case, firing from sensory neurons activated by innocuous stimuli is now perceived as pain.
