So were it not for weed they would not have been addicted to meth? Is that what you are going with?
Of the 2, what is more likely to lead to addiction to "hard drugs".
An alcohol drinker, who does not smoke marijuana? Ever.
Or a recreational marijuana user, who if in a non legalized state, is obtaining their weed from a drug dealer, and is around other people who may already be using or have access to "hard drugs"?