If one is predisposed to smoke pot, it seems it would follow that one may be predisposed to move onto other drugs..but then again maybe not.
I know a few potheads who are just that....potheads.
How 'bout parents and their peer group chain smoking cigarettes (for the early boomers before the first Surgeon General's report.) I'm partial to a 'what's on the menu' (what's not.) narrative for addiction (and gender deviancy). A lot of us spent much of our lives wrapped in a cloud of second hand cigarette smoke. Libertarianism makes for really insightful polemics, but in real life it's probably best to protect young'uns from smoke, porno and generally trashy media influence. Thank *** I never bred none in the present culture.
I have met hundreds, perhaps thousands, but I have yet to meet anyone who has used heroin.