Sweden has a long history of strong legislation and rhetoric against all kinds of drugs (except alcohol and tobacco of course). This lead to some pretty strong advertising of the type "One marijuana will leave you a mindless and desolate husk! Don't do any of the marijuanas!". Shown in schools even.

Because of the propaganda to science ratio, this had the awkward effect on people who nevertheless ended up trying weed that they sometimes assumed that the authorities must have been lying about the other drugs as well. So, "Weed didn't kill me. I guess the other stuff is a lot less harmful than they made it out to be as well".