Hundreds of millions of people around the world experience chronic pain – meaning pain that lasts longer than three months. While the numbers vary from country to country, most studies estimate that about 10% of the global population is affected, so more than 800 million people.

The Centers for Disease Control and Prevention estimates that in 2021, about 20% of U.S. adults – or more than 50 million people – were experiencing chronic pain. Of those, about 7% experienced what’s called high-impact chronic pain, which is pain that substantially limits a person’s daily activities.

In the past, physicians have been quick to prescribe medication as an easy solution. But the opioid crisis in the U.S. has led doctors to reevaluate their reliance on drugs and look at new treatments for patients with chronic pain.

The Conversation spoke with Rachael Rzasa Lynn, a pain management specialist from the University of Colorado Anschutz Medical Campus for our podcast The Conversation Weekly. She explains some of the new developments in pain treatment and why there’s hope for patients with chronic pain.

What is the cause of chronic pain, at the most basic level?
In general, pain is a complex interplay between tissue injury or inflammation, nerves and brain processing.

There are several different biological processes that can result in pain. The one that’s happening to most people when they experience acute pain is called nociceptive pain. This is pain that occurs when tissue is being injured or potentially harmed in some way, which triggers the activation of surrounding nerves. These nerves are like electrical wires that send signals from the injured tissue, through the spinal cord and to the brain, where pain is ultimately perceived.

But activation of those nerves alone does not equal pain, because those electrical signals are amplified or diminished at multiple points throughout their transit to the brain. The brain’s perception of pain is critical because pain does not occur when people are unconscious.

Nociceptive pain can also result from ongoing tissue injury or inflammation, as in the case of arthritis. With these injuries, the peripheral nerves are chronically reporting to the brain, resulting in an ongoing perception of pain.

There are other disease processes, such as diabetic peripheral neuropathy, in which nerves themselves become injured. In these cases, the nerves send pain signals to the brain that are reflective of injury to the nerves themselves, not the tissues they report from. This is called neuropathic pain.

In other forms of chronic pain called nociplastic pain, the initial tissue injury may fully heal, but the brain and nervous system continue to generate pain signals.

Many chronic pain conditions actually involve a combination of all three of these phenomena – nociceptive, neuropathic and nociplastic pain – which adds to the difficulty of diagnosis and treatment.


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