One note: My housemate, in all his decades of counseling and teaching never observed ONE case where an addict of any kind was lacking a significant degree of RAD--Attachment Disorder from the first 6 years of an unbonded, unconnected life. And, that does NOT mean that the parents didn't love the child.
As other research has indicated, it does likely indicate that the child did NOT FEEL loved.
RAD could be the worst condition in the world for a child to have. Better to have a terminal disease than an inability to love. I don’t doubt that a total lack of empathy and often morality contributes to a general decline in self care, and then thus makes addiction less of a boogeyman to avoid (because you just don’t care). I don’t think it specifically leads to addiction. As ruinous as it is to the individual and those who attempt to love or care for him.