I don't think he has a "problem". I was the same way. It works like this: the drug plus alcohol will "open him up" energetically.. when he "comes down", his consciousness falls lower that it was prior .. if he is sensitive or is a spiritually minded person it'll be a bad come down. In addition, past trauma will come forth when he opened up so feelings of despair and depression even powerful panic attacks can be common. Some people who are on a lower level of consciousness can do quite a bit of drugs and alcohol no problem.
If I get smashed one night, next day I feel horrible, depressed and very very unpleasant. It would take me 3 full days to feel "normal" again. So I can relate. How about he skips the drugs and maybe cut down on alcohol. Or maybe find new friends that enjoy other things.. just a thought.