I have to respectfully disagree.
There are numerous examples of those with brain trauma being successfully helped with or the effects of years of stress and/or depression (another form of trauma), to state nothing of the complicating factors of drug (legal or otherwise) and alcohol abuse.
https://www.rewireme.com/brain-insight/5-myths-ptsd/
The relatively-new field of study is referred to as Neuroplasticity.
2 conflicting references and a 3rd supporting recovery:
http://healingtraumacenter.com/neuroplasticity-and-rewiring-the-brain/
https://www.psychologytoday.com/us/blog/workings-well-being/201703/how-heal-the-traumatized-brain
For the OP, this is pertinent to starting the healing journey, but I concede that you have an uphill battle to get your son to admit some small steps can change how he feels:
https://www.jennifersweeton.com/tools/
My entire frontal lobe was turned to hamburger.
There was an empty hole as big as my fist until scar tissue? formed, years later.
Temporal/occipatial lobe damage, as well.
Total anosmia, to boot.
It was a miracle I did not die.
11 day coma “only”.
Mostly intact but I have memory issues galore, mild absence seizures and neurological deficits.
This was back in 1981, when all they really did was strap you down and hope you didn’t die.
Things are probably better now, medically, but the craptastic “doctor” I had was barely more than useless.
I had NO support from family and no therapy.
My mother was pissed that the money spent on my hospital stay meant she didn’t get her usual annual new car.
Seems y’all are more willing to make sure your boy doesn’t wind up like me.
Have hope.
In spite of everything no one bothered doing, I actually got smarter.
“Changed” into a person who wanted to learn about “crazy stuff” like quantum physics and learned Greek to read the NT.
Before, I just wanted to party and see bands.
Probably the ‘rewiring’ effect.
So, maybe the difference will be the support he’s getting.
Hope so, anyway.