That’s a retarded little stat. Kids that don’t see a drug as harmful probably do drugs (more than just pot) and therefore can have a problem, kids that see the same drug as harmful probably don’t do any drugs and therefore can’t have a problem. So yeah kids that do drugs are indeed more likely to have drug problems than those who don’t, that doesn’t mean the particular drug in question (pot) is harmful.
Well if the numbers don't do it for ya how about the links I posted on the harmful effects of pot...