well i smoke a lot of weed most of the time and i can say that even though i have tried a couple of other drugs once i have been able to say no many many times when offered again. the great thing about weed is the more you smoke it the more rational you become. its kind of weird to explain it without someone taking it but basically at first i think someone is more likely to jump to other drugs through it because it inebriates you in a similar way to alcohol but unlike alcohol over time you get used to the drug and then you pretty much act how you would normally except more focused on what your doing (which is great when working on a project or driving for example)
so in conclusion i think it depends how long you have been on the drug
so in conclusion i think it depends how long you have been on the drug