"Bipolar Rule Numero Uno: When its good its very very good but when its bad its HORRID"
I first wanted to say welcome to healing well. I am sorry about your son's accident and diagnosis. I know it is hard. He is lucky to have a caring and supportive mom as yourself.
There was just one point I wanted to make here and that was that I believe that it is entirely possible that your son's mental illness could be wrapped up in chronic pain. This I believe would be due to the fact that he was in a severe accident and then subsequently diagnosed with bipolar disorder. These two things combined together can have a devastating effect on someone emotionally even after the physical injuries have healed. It is very important to remember that when you are dealing with any mental illness and in particular bipolar disorder it is really based on an individual basis, meaning that everyones symptoms and perceptions will be different.
My thought go out to you and your son.