I understand your concern towards your friend. More clarity is needed regarding his problem. Weed / nitrosun etc. are nervous system depressants which have the ability to cause all sorts of issues including anger dyscontrol, depression, anxiety, psychosis or even dementia. It is unclear since when he has stopped using them. However it is easily manageable with appropriate treatment, so that dysfunction due to the same can be reduced and his quality of life will improve. Some counselling sessions along with medical help might be useful for him. I suggest you take him to a nearby psychiatrist for detailed evaluation. I would also be more than happy to help you with that if you are looking for online assistance. My clinic is at OMR chennai. Discussions will be held confidential. You can directly consult with me through Practo as needed. Online chat consultation is also available.