My answer is you know your friend and his situation better than anyone in this forum. If your instincts said to tell his parents and you did it for the right reasons (protecting your friend) then there is nothing else to be done or justify in my honest opinion. When I was in college we hung out in a big group much like the QLSG. We had a friend who drank ALOT and then he would drive his motorcycle -and drive it very recklessly. We knew it. We talked about it and we talked to him about it but thats as far as we went because we were his "friends". Last day of classes our senior year he got drunk and drove that bike right into a cement pole and was killed instantly. I will never forget that night and I will always wonder if we should have (could have) done something to stop him from drinking and driving. So thexonic - sometimes being a best friend means doing the hard thing not the easy thing. You might lose a friend - but hopefully only temporarily and not permanently like I did.

What a strange illusion it is to suppose that beauty is goodness.
~Tolstoy~