YES!
I had not seen my eldest son for maybe 2 months.
He had not told me he was taking drugs!!!
When he came to have Christmas lunch, I had to hold onto the kitchen bench, from the sheer shock of how he had become very thin.
After that, I keep an eye on him, all the time and that was 15 years ago.
He never uses now, and has put on weight, but I just did not forget that Christmas....and we did talk in depth about it, later.
No parent should ever go through it! but sadly it happen's.
I will say it took a long time for the shock and pain to wear off.
He stopped, and I was Most grateful!