It may not have anything to do with drugs. Or, perhaps he parties to cover up a massive depression. Regardless, Hollywood is a very lonely, soul sucking place - and, as they say, it is lonely at the top. Many people who have a very serious depression- to the point of suicide- give the appearance of being okay. Comedians seem especially prone to this - mask the pain with laughter. Richard Jeni is a recent example of this. Owen is not one of the ones who courts the tabloids, and that makes me sad for him that this will garner so many headlines. It's part of the business, but he's a brilliant mind and obviously is going through a very difficult time, regardless of the cause. Can you imagine having so much private pain that you've actively tried to hide that you'd want to end your life - and then the embarrasment of having it all made public? I hope that he does the healing and soul searching that he obviously needs to do. I've always liked him a lot.
When I read about this, I couldn't help but think of one of my favorite movies - The Royal Tennenbaums - which Owen co-wrote. The character, Richie, attempts suicide by slicing his wrists. It makes you wonder how much of Owen was in that part.
I'm usually all for speculating, but this... this is just too personal and private, imho- at least for me. My prayers are with you and your family, Owen.