Why do some individuals suffer long term pain while others don't?

I am interested in neurophysiological mechanism that impart vulnerability to develop chronic pain conditions. One potentially important factor is the correct functioning of endogenous pain modulatory circuits that link the brain and spinal cord to powerfully affect pain processing. Currently, I am investigating the causal link between injury induced brain network reorganisation and the development of the pain state in pre-clinical animal models of persistent pain. I try to take findings from clinical studies in human patients (e.g. fMRI studies) and investigate 1 - whether the pre-clinical models are able to recreate these features and 2 - how they causally relate to sensory, affective and cognitive disturbances that develop following injury.