Beware of the Choking Game. It is so sad. The daughter of friends of ours died from that. The think that is scary is that it is really good kids who are getting caught in the lure of having a "high", but not doing anything illegal.
Be aware of signs...marks on their necks, rope or fabric tied to drawers, etc. in their room...watch your kids. It's bad when they do it with friends, however, most fatalities occur when they try to do it when they are alone. They walk a fine line and then can't get back.
Sounds horrible...