Re: Marijuana
it might have, but its like saying that gravity may have different effect on different people so it might be ok for someone to jump from 10 story building.
There are few things whose effects are certain with large degree of confidence. Poison, bullet, drugs and all. There are things that are ok but for some people, they might be a killer. like fat, sodium, sugar ..
what is certain is haraam for all, what is specific to certain people is haraam for them only.