an excerpt that I feel many here have stated as well:
The whole thing can get very complicated. For one, the teenager who is trying to continue his addictive lifestyle will naturally play one parent against the other. He will be aware of the tensions and resentments being played out. In fact, as both parents desire to win his approval, playing one parent against the other will bring him more and more power.
And secondly, the teenager is probably going to side with the parent who is most enabling of him in his addiction. The one that most wants to rescue him from the consequences of his addiction is naturally going to be the teen-favorite. Sometimes, but not always, the enabling parent has a relationship with substances too. Therefore, he or she minimizes the seriousness life-threatening nature of the teenager's addiction. Often, there is a whole lot of drama and finer-pointing. Through it all, the teenage drug addict wants the focus to be on the parents, not on him