Why Pain Becomes Chronic
Pain usually serves a useful purpose. If we injure a joint, muscle, or bone, pain tells us that something is wrong and encourages us to protect the injured area while it heals.
But sometimes pain continues long after the original injury should have healed. When pain lasts for three months or longer, it is generally considered chronic pain.
Pain Is More Than a Signal From an Injury
We once tended to think of pain as a simple warning signal: damaged tissue sends a message to the brain, and we feel pain.
Researchers now understand that it is more complicated. Pain is produced by the nervous system and influenced by signals from the body as well as the brain's interpretation of those signals.
With persistent pain, the nervous system can become increasingly sensitive. Signals that once caused little discomfort may begin to hurt, and pain may continue even when there is relatively little ongoing tissue damage.
This does not mean the pain is imaginary. The pain is real, even when an X-ray or MRI cannot fully explain it.
Why Does This Happen?
Chronic pain can have many causes. Arthritis may continue to irritate a joint. Nerve damage can produce burning, tingling, or shooting pain. Previous injuries, surgery, inflammation, and some medical conditions can also contribute.
But pain can also be affected by poor sleep, physical inactivity, stress, mood, and fear of movement. These factors can interact with one another. Pain can interfere with sleep and activity, while poor sleep and inactivity can make pain harder to manage. See the section on Sleep & Insomnia for more about the importance of restorative sleep.
Can the Brain Learn to Reduce Pain?
An intriguing approach called Pain Reprocessing Therapy (PRT) is based on the idea that, in some people, chronic pain continues because the brain interprets otherwise safe signals as threatening. Treatment attempts to help the brain reinterpret those signals as safe.
In a randomized trial of 151 people with chronic back pain, 66% of those assigned to PRT were pain-free or nearly pain-free after treatment, compared with 20% receiving a placebo treatment and 10% receiving usual care. Most of the improvement persisted at one year.
Even more interesting, a five-year follow-up found that 55% of the PRT group remained nearly or completely pain-free, compared with 26% of the placebo group and 36% receiving usual care.
These are impressive results, but they need perspective. The original study involved people with a particular type of chronic back pain in which a clear physical cause could not be identified, and the participants averaged about 41 years old. We do not yet know how well these results apply to other kinds of chronic pain or to people in their 70s and 80s.
Pain Reprocessing Therapy was developed in part by Alan Gordon, founder of the Pain Psychology Center and co-author of The Way Out. His work offers an interesting example of the growing effort to treat some chronic pain by changing how the brain interprets pain signals.
See Emerging Treatments for Chronic Pain for more about Pain Reprocessing Therapy and other approaches being investigated.
Why Understanding This Matters
If chronic pain were always caused by continuing tissue damage, the solution would simply be to find and repair the damaged tissue.
Often it isn't that simple.
That helps explain why chronic pain treatment increasingly combines approaches such as appropriate exercise, physical therapy, medications, better sleep, and psychological or mind-body techniques rather than relying on a single treatment.
The encouraging part is that the nervous system is adaptable. For some people, gradually increasing movement, improving sleep, reducing fear of activity, and learning ways to change the response to pain can improve function and reduce pain.
There is rarely one answer that works for everyone. Understanding why pain has become chronic is an important first step toward figuring out what may help.
Learn More
NIH — Pain
A thorough explanation of acute and chronic pain, including how changes in the nervous system can make people more sensitive to pain.
https://www.ninds.nih.gov/health-information/disorders/pain
MedlinePlus — Chronic Pain
A clear overview of chronic pain, its causes, treatments, and ways of living with persistent pain.
International Association for the Study of Pain — Living With Pain
Patient-oriented information and resources for people living with chronic pain.
Video
Mayo Clinic — Central Sensitization Syndrome - 22 Minutes
An explanation of how the nervous system can become sensitized and how this can contribute to chronic pain.