Retraining the brain to treat chronic pain

The researchers tested an approach to treating chronic back pain for which no physical cause could be found. StratfordProductions / Shutterstock

More than 25 million people in the U.S. live with chronic pain, defined as pain that lasts for more than three months. Despite costing the health care system more than $600 billion a year, existing treatments for chronic pain fail to provide relief for many people.

The most common type of chronic pain is chronic back pain. In about 85% of cases, no physical cause for the pain—such as arthritis or disk damage—can be found. Such unexplained pain is thought to be caused by brain changes after an injury that persist even after the damage heals.

These changes in the brain are thought to serve an important purpose immediately after tissue damage. They provide a warning signal to restrict movement and let the body recover. However, if they continue to send that signal after the injury has healed, the result can be chronic pain.

Researchers have developed a type of treatment called pain reprocessing therapy (PRT) to help the brain “unlearn” this kind of pain. PRT teaches people to perceive pain signals sent to the brain as less threatening. Therapists help participants do painful movements while helping them re-evaluate the sensations they experience. The treatment also includes training in managing emotions that may make pain feel worse.

For the first clinical test of PRT, a team at the University of Colorado, Boulder led by Dr. Yoni Ashar (now at Weill Cornell Medical College) and Dr. Tor Wager (now at Dartmouth College) enrolled 151 people with mild to moderate chronic back pain for which no physical cause could be found. Participants received one of three treatments: four weeks of intensive PRT, a placebo injection of saline into the back, or a continuation of care as usual.

Participants rated their pain before and four weeks after starting treatment. They also underwent fMRI scans to look at brain activity before and after treatment. The team followed up with participants one year later.

The study was funded by NIH’s National Institute on Drug Abuse (NIDA), National Institute of Mental Health (NIMH), and National Center for Advancing Translational Sciences (NCATS). Results were published on September 29, 2021, in JAMA Psychiatry.

After 4 weeks of PRT, 66% of people who underwent the therapy reported being pain-free or nearly pain-free. In contrast, only 20% of people who received placebo injections and 10% of those receiving usual care reported similar improvements. The reductions in pain after PRT were largely maintained a year after treatment.

The fMRI scans revealed that, compared with the other two groups, people who received PRT had substantial reductions in brain activity in several regions associated with pain processing.

“For a long time, we have thought that chronic pain is due primarily to problems in the body, and most treatments to date have targeted that,” Ashar says. “This treatment is based on the premise that the brain can generate pain in the absence of injury or after an injury has healed, and that people can unlearn that pain. Our study shows it works.”

“This isn’t suggesting that your pain is not real or that it’s ‘all in your head,’” Wager notes. “What it means is that if the causes are in the brain, the solutions may be there, too.”

The volunteers were relatively well-educated and physically active. Further studies are needed to assess the approach in more diverse populations and with other types of chronic pain.

—by Sharon Reynolds