@aviva - I think it's wonderful that you and your daughter have such an open relationship. It's important to be open and honest with our children in order to gain their trust with such sensitive subjects.
I work in the emergency room of a very large hospital and I can't tell you how many cases of self-induced hypocapnia I've seen among children, some as young as six years old.
The Center for Disease Control recommends that health care providers as well as parents and teachers become familiar with signs of the games evidence.
Physical signs on the body are markings on the neck and bloodshot eyes. The child may have severe headaches and a sense of disorientation after being alone for awhile.
Listen for any discussions about the game and watch for any unusual conditions in their room like ropes, belts or scarves tied to furniture or doorknobs or knotted up on the floor.