What you are describing is a situation where pain and other symptoms last beyond the expected time for healing. After four years, it’s safe to say this kind of clinical presentation can be labeled as chronic pain.
Newer research over the last 10 years has shown that some people catastrophize their symptoms. This means they stay focused on their pain (sometimes obsessively and in detail). They develop helpless behaviors. This means they believe they can no longer engage in activities and function because of their pain.
At least one study has linked elevated cytokines with catastrophizing. Cytokines are signaling molecules used in cellular communication. People who catastrophized had higher levels of interleukin-6 (IL-6), a specific type of cytokine. The results suggest that mental and emotional responses during pain experiences can lead to inflammatory immune responses. And using scores from a tool called the Pain Catastrophizing Scale might be a way to predict IL-6 reactivity.
The authors of that study conclude that in some people, pain appears to cause a release of extra proinflammatory messengers that turn up the nervous system’s sensitivity. The result is an amplified (louder) broadcast of pain messages to the brain. So, we know there may be an inflammatory response as the main mechanism by which catastrophizing shapes pain responses. But we still don’t know the exact way in which catastrophizing turns on the cascade of steps leading to inflammation.
Clearly, there is a link between psychologic processes and central pain processing. Screening patients for catastrophizing might help identify patients at risk for this immune-based pain response. The next step is finding a way to turn it down or off to prevent a chronic pain response from developing. Your friend might be able to benefit from the results of that last type of treatment if and when it comes available.