question

Of course is possible. I've been doing this shit and in day 4 or 5 you feel that the brain fog desapears. Sadly these days I have destroyed my hole reboot, but,
it's now or never

 

There's not a lot of research into it, but from the limited studies I've seen that depends on a couple of things.

I'm sure you're aware of the side effects from severe addiction such as shrinkage of the brain, and damage to the prefrontal cortex among other areas. Through time and abstinence the brain slowly rewires itself around those old pathways and tries to correct the damage you did, and it's luckily not like alcohol where a lot of cells usually die and don't grow back in the brain. The longer you stay away from an addiction the more your brain bounces back, by making an effort to fight back and actively try to use rational thinking that helps restore areas that were injured from abuse.

The biggest issue I can think of is if you got addicted before you reached adulthood, and your brain is still growing. When growing up your brain is shaped by what you take in, so one would think that if someone is going into puberty with an addiction they would have lasting implications since a lot of that is hardwired into the brain.

 

It depends on what you mean by brain damage. I don't know about physical brain damage. I know that I spent most of my life filling my brain with trash. Do I think that my brain will ever be like it was before, no.