What you CAN'T do:
Stop him... or convince him to stop. It's not your "call," dear Shari, truly. That one's purely on him... I am quite sorry to say. People don't stop destructive behavior until THEY want to stop... for whatever are THEIR reasons... not because you (or someone else, even the law) are fearful for him/want him to stop. It just doesn't work that way.
What you CAN do:
LOVE him... to the best of your ability... and be there... when he stops... without reservation. Taking "care" of him, however, won't work. It just makes it easier. True, you don't want your baby to freeze out in the cold, but a warm blanket, rather than a invitation back into a warm bed... might serve to "wake him up" quicker. You may not be at that drastic of a point yet, but if you get there...
Also, keep your car keys near you, because lack of driver's license has never stopped anyone who wanted to drive from doing so... particularly teenagers... whether they drink, do drugs, or not. When a young wants to go, they find a way.
Please, if he was your son, what would you say to him?
I would secretly pack his/her stuff, take it outside, then invite him/her outside, look him/her straight in the eye and say:
"You know I love you, don't you? No, seriously, don't tell me what you think I want to hear... tell me the truth: you KNOW this, yes?"
If the answer is "yes", then I would say:
"Well, because of that love... I can't watch this. I cannot sit back and watch someone I love this much... self destruct like this. It will kill me... and I can't help you if I'm dead. So, you're either gonna have to stop... or stay away. 'Cause I won't watch it. I can't. You want to live your life and do your thing... cool. I understand that. Who doesn't? But I love you... and I won't help make it easy for you to harm yourself. I couldn't live with myself if I knew I'd done that. So, here's your things... go for it. Live your life. But if you decide to come back in the house... you leave your problem outside. Get help, fine, do whatever... but I don't ever want to see it again."
If the answer is "no", then I would say:
"Well, I do. And if I haven't shown it enough, tell me what I need to do so that you DO know it. In the meantime, this thing that you're doing... I can't watch it. I cannot sit back and watch someone I love this much... self destruct like this. It will kill me... and I can't help you if I'm dead. So, you're either gonna have to stop... or stay away. 'Cause I won't watch it. I can't. You want to live your life and do your thing... cool. I understand that. Who doesn't? But I love you... and I won't help make it easy for you to harm yourself. I couldn't live with myself if I knew I'd done that. So, here's your things... go for it. Live your life. But if you decide to come back in the house... you leave your problem outside. Get help, fine, do whatever... but I don't ever want to see it again."
And then I would walk back into my house... and shut the door.
And if they come back in, I would hug them and cry with them... and thank them for that decision... and ask them what I can do to help. Then I would thank JAH.
If they did not come back... I would go into my room, approach JAH... and ask Him to let my Lord carry this burden for me... and put it is his hands.
Have I thrown my child out? No... I have simply given him/her a CHOICE... and it is entirely up to him/her to make it. And THIS would be, for them, the true beginning of being an "adult", one responsible for oneself.
I hope this helps, my dear, dear Shari. My love... and prayers for peace in your household... to you!
Your servant, and a slave of Christ,
Shel