One of my first posts on this blog in 2018 was about brain tricks. Four years later there is way more information about the role of predictive coding in different conditions, including chronic pain. Some of the researchers involved in this are: Tor Wager, Mick Thacker and Zhe S Chen. The idea is that there is a top down processing of pain in various areas of the nervous system and a bottom up flow of information from the periphery to the brain. The ultimate goal of the humans is to survive and predicting future events increases the chance of survival. The best way to look at pain is to consider pain as a danger signal. Sometimes the nervous system gets stuck in predicting pain when there is no actual threat. The theory is that the prediction is so strong that it does not matter what signals are coming from the body.
In my opinion it is not only that the prediction happens but also the body is affected. There is a prediction error generated whenever the prediction does not match the actual input from the body. I don’t think prediction errors are tolerated in the nervous system for long periods of time. So the options are either change the prediction or change the input. The prediction obviously does not change as long as there is chronic pain. Then the only option is that the input changes. Our nervous system has amazing control over the body. I think it is reasonable to assume that the brain can actually change the input to match the prediction in chronic pain through a variety of mechanisms (e.g. autonomic nervous system and immune system). There is a paper by Moseley et. al. in which they show that an illusion of the hand location in complex regional pain syndrome can change the temperature of the hand. Asya Rolls has published articles showing the connection between the brain and the immune system. In one paper by Koren et al. they show that an inflammation in the colon activates certain brain areas and then activating the same brain areas can create inflammation in the colon. In the end it is likely that there is both a body and a nervous system problem in chronic pain. But the cause is probably the nervous system.
The best way to change the prediction is actually psychotherapy: see the work of Howard Schubiner. The psychological approaches are pain reprocessing therapy (PRT) and if needed, emotional awareness and expression therapy (EAET). In the real word it is a little hard to convince patients with chronic pain to explore the psychological approaches that can significantly improve or even cure their chronic pain. Our society is so focused on structural problems that we have become oblivious to the role of the brain/nervous system.
There are also ways to affect the bottom up information. For example, movement therapies like physical therapy, yoga, tai-chi can change the actual peripheral information. There is a chance that the weight of this bottom up information will increase over time when compared to the prediction. Slowly the prediction will move closer to the now improved peripheral information and chronic pain disappears.