This could have been written ɓy me when DS was 17 (apart from.the illegal drugs). He refused to attend appointments with CAMHS, dropped out of 6th form, was horrendous to live with to the point of me becoming suicidal and having to take Citalopram. He was also suicidal, chronically depressed - never left his room, didn't eat, screamed at us whenever we tried to engage with us etc etc.
He's now 28, has completed a 3 year apprenticeship and is in a job he loves. He's an absolute delight to be with, he lives 80 miles away but comes to visit us regularly. He phones for a chat a couple of times a week.
I really can't believe he's the same person. We had to endure 3 years of hell at home, he moved out when he was 20 and sorted himself out. He needed space from us and us from him.
I know it's really hard to hang in there when your child is going off the rails. We didn't throw him out as I felt that, if we did, he would sink without trace and never come good. However, I would never blame a parent who made the decision to evict their (adult) son or daughter.
No particular advice I'm afraid, but in DS' case it all came good. He sometimes reflects back on those days and admits that his behaviour was horrendous and abusive. He has apologised, and we have accepted that apology because we believe he was incredibly unhappy as a teenager.