Hi! I have been involved in addictions counselling as a social worker for many years. There is, or there maybe, a genetic component to addictions. A “Predisposition”. However, it doesn’t follow on like night to day, that the person with a genetic disposition WILL become a drunk or a crack head. An individual;'s addiction to drugs or alcohol owes as much, even more to learned behaviour that is to say, if you see your daddy or your mummy getting caned every day you may believe that that is what all grown-ups do, all the time. It also depends on whether one possesses a strong will and mind of one’s own and so can make choices for oneself.
This is of course a rather simplified schema and the mechanisms that lead to addiction or not addiction, are very complicated and, in fact, are not fully understood.