Suppose an individual has fallen off his motorcycle and injured his back several times. He has gotten drunk and jumped from cliffs into lakes. He has rolled his four-wheel drive vehicles, fallen down steps, and gotten into bar fights_but he now falls off a forklift and his back is suddenly worse_that is an exacerbation of a pre-existing problem.
You can reasonably argue that if he had used reasonable care and judgment earlier in life, the forklift injury would not have been so severe. (You could also argue that if he had not stayed out the night before drinking that he would have been more careful at work on the day of the injury.)
However, many injuries are cumulative.
If depression occurs in an individual who was victimized as a child, delinquent as an adolescent, abusive as a adult and irresponsible as a parent, friend or worker.
What then is exacerbation of depression? What should be treated is depression that arises because of the injury, not for the resolution of his longstanding marital, addictive, childrearing, legal and financial problems.
In this case, what is needed is a careful delineation (precise and complete evaluation) of what has arisen solely as a result of just this injury, and how that is best treated.
For this patient, a return to pre-morbid functioning means aking him emotionally intact in ways he was prior to injury, just returning him to baseline. What cannot be done is the creating of a life for him that he never had.