I think it is important to realize that there is a difference between being, well, 'crazy' in the irrational sense, and being utterly insane in the real meaning of the word.
The legal profession in the US defines insanity as an utter break with reality. No connection to it at all, meaning that a person can no longer distinguish between right and wrong. How can you tell?
The foundation of the insanity is the inability to experience doubt or guilt for what one is doing. So, when the police show up, you don't hide from them... because you don't think you are doing anything wrong. There is no 'guilt factor' in your behavior, such as trying to hide the evidence or obscure what has been done.
When someone goes to great lengths to justify his actions and cover over his actions, he is not insane. Someone can have severe mental illness, but that does not make him truly insane if he can still distinguish right from wrong. People with mental illness, by definition, are not 'immoral.' They are also not 'amoral.'
Neither is the addict. In fact, the addict's greatest burden is his own fight with his morality. The conscience is the 'enemy' of the addict, reminding him of what he has done and how wrong it was to do what he did. The struggle with the conscience can lead to 'insane,' or more accurately, illogical and stupid, behavior. But, the addict is not insane. He is troubled, but he still knows right from wrong. otherwise, he would not need to medicate himself with his addiction.
Very few people cross that line into utter insanity, and they are never brought there by addiction. An addict by definition is 'sane' in the sense that he is always (even under piles of denial) acutely aware of right and wrong. He suffers from addiction because of his sanity.
The Big Book of AA speaks of recovery as being 'restored to sanity,' but this is not meant to say that the addict is one who has lost all touch with reality. It is a metaphor for the restoration of one's integrity, where the man lives according to his conscience, and his conscience is in harmony with the divine will. Man does not enter into true 'sanity' until one enters into relationship with God.
By extension, the further one moves away from God, the more 'insane' we become. We have a harder and harder time distinguishing right from wrong as we depart from God in our minds.
In the Orthodox Church, there is a belief that even severe mental illness does not interfere with this relationship. We have numerous saints with mental illness, sometimes called 'Fools for Christ.' There are some saints who faked mental illness as well, using the treatment at the hands of others and the embarrassing side-effects of such illness to curb their pride. But, in the end, they were all people who were close to God.
The recovering addict has this same potential to connect with God, though his 'insanity' is largely curable. This is not to say that it is entirely curable, as those with long-term sobriety can attest. And so, what remains is part of one's struggle to meet God, and like the 'Holy Fool' who encounters God even in the midst of mental illness, so the addict encounters God even in the midst of his broken humanity.