If two people sustain the same type of injury or undergo the same surgery, one may heal normally, while the other continues to feel pain for months or years. In other people, chronic pain develops independently of any detectable damage to the body. Why do some people develop chronic pain, while others do not? Researchers have done many studies looking for the answer to this question.
It is important to note that while science is good at finding correlations, or apparent relationships, between factors and health conditions, correlation does not prove that the risk factor causes the health condition. Many risk factors for chronic pain have been identified and are being studied, but none have been pinpointed as the cause of chronic pain.
Some scientists who study pain theorize that in some cases of injury, surgery, or shingles (herpes zoster) outbreak, the acute pain felt at the time of the event changes the way the brain and nerves function, sensitizing the nervous system to keep relaying pain messages and causing it to lose the ability to modulate pain sensations. People with higher levels of acute pain are more likely to develop chronic pain. Scientists theorize that rapid and effective management of acute pain may result in fewer people developing chronic pain.
Psychological response to pain seems to play a role in how pain is felt. People who have more anxiety, distress, and fear related to acute pain seem to have a higher likelihood of developing chronic pain. It is theorized that the chemicals the body releases in response to these emotions increase pain sensitivity.
There is not a "chronic pain gene," but researchers have identified several genes that are thought to play a role in how pain is felt. For instance, sensitivity to pain and ability to tolerate pain may be inherited. Some studies suggest that chronic pain conditions may run in families. Certainly, family medical history does raise the risk for some painful health conditions such as endometriosis, rheumatoid arthritis, and spondylitis.
Women are more likely to develop chronic pain than men. Studies show that women tend to have a lower pain threshold and a lower ability to tolerate pain than men. Women seek treatment for chronic pain at a higher rate than men. Research is underway to determine whether estrogen, the female sex hormone, influences how pain is felt in women.
Risk factors for developing chronic pain include: