Something to consider: perhaps these people became addicted when they discovered that opiates provided relief from underlying depression... I have a feeling this may be one reason why some get addicted and others don't. (Believe it or not, some people even dislike taking opiates!)

disclaimer: I am kind of obsessed with the self-medication theory of addiction

When I was suffering from bad back pain, the amount opiates that was being written for me was ridiculous.

I refused to take it, the side affects, even in the short term were awful.