In the case of a pain disorder, the individual *interprets* the pain as so great that he/she is unable to work or function within society. The patient with a pain disorder allows the condition to interfere with job and relationships.
(a) Many people arise each day in pain, most often back pain. They go to work,engage in recreational activities, maintain relationships, rear children and contribute to society.
(b) Others, with the same complaints, stay home, watch TV, take prescribed narcotics, and insist that they can never work again. It is that difference between (a) and (b) that determines a pain disorder or, in some cases, malingering.
There is not a physical measure to determine which pain will lead to a pain disorder. There are psychological ways to determine that difference. Chief among these are the person’s goals and motivation.
Thus, if you have two patients with identical back injuries/damage, it will be the *psychological* factors that determine which patient will mobilize and become productive versus the patient (pain disorder) who does not do so.