This seems to be too common. It wasn't all that long ago that River Phoenix died of an OD.
Perhaps it's an indication that when you are fabulously overpaid and showered with adulation and adoration all over the world essentially because you are either rather good at pretending you're someone you aren't or you are related to someone who has demonstrated such an ability in a saleable way, that eventually the shallow lie that is your life becomes just a bit too much to bear and you seek an escape from it. It must be difficult, sometimes, for people to come to the realization that they haven't truly DONE anything with their life other than perhaps being someone who has found a saleable signature phrase, has a particular glint in their eye or something equally vacuous.
Sorry, I'll stop my rant :-)