I definitely think there is such a thing as an addictive personality. We know that babies born to an addicted mother are born with that addiction (alcohol fetal syndrome, heroin, etc) so we know that some of it is passed genetically. I don't have stats, but know first-hand many alcoholics who had alcoholic parents.

I also believe that eventually the drug takes over and takes control, whether it be hard drugs, alcohol or nicotine (or caffeine or even the adrenaline rush of gambling) so that when you're trying to deal with the person inside, you can't really reach them until the drug is out of their system. Until then, you're just talking to the drug, which won't be reasoned with because all it knows is that it wants more.