Yes it was his choice to initially take drugs and yes he had put himself at risk of addiction. However he started abusing drugs at thee age of 13 and I personally think that is very young and a child-because that is what he was may not understand/underestimate the gravity of this decision they have made. He was especially young to have started drugs and I think it would be fair to say that if something started so long ago when you were still a child then it may be hard to loosen the grip of it. He had tried rehab clearly with varying degrees of success and in spite of his demons built a successful career and loving relationships not only with Lea but as a friend to many people.
He is not the first to start so young, Drew Barrymore is one. I think if you have that in you then you are in trouble.