What Is The Treatment For Acquired Brain Injury In A 20 Year Old?

My 20 yr old son with acquired brain injury (frontal lobe,pariatal,occiputal) has been smoking cigarettes for about 4 years, and has been using pot to get to sleep every night. We have seen a drastic change in his personality, and he seems totally unmotivated. His brain injury happened when he turned 11. What information do you have on the nagative effects of using pot with brain injury??