Why modded -1? This study supports other studies that came to similar conclusions:
Yes. Marijuhana-abuse by minors is a big problem. Not if done once, but an abuse, that does not affect grown ups (from 21 or better, 25 years on) very much has a devastating effect on their brains. The reason, as I understood it, is the rearranging of the whole brain structure while being juvenile. This rearrangement, as new scans showed, is much more fundamental than previously known. And smoking grass fucks that up big time. And it messes with the hormon levels. Those rearrangements possibly can not take place after the normal timeframe. If they were haltet or obfuscated by marihuana abuse, those youngsters have a permanent brain damage.
But: Abusing any brain affecting drug in that time will possibly do the same, so drinking alcohol instead of smoking is not an option. If I had children, I would insist on limiting marijuhana use to one time pet year, four times max until they are 21 (you are an adult at 18 here, so a bit of cooperation from the other side would be necessary. Any smoking of marihuana under the age of 16 would be completely out of the question.
Your war on drugs was one big mistake. But inform yourself before letting your kids use it limitless. If those studies are right, they suggest that using marihuana (esp. in a vaporizer) is indeed less dangerous than alcohol for the body. And does not effect grown ups as much as heavy drinking would. Even really heavy abuse does not make you significantly dumber, just a measurable bit and it is possible that the brain could recover, except for some problems with the short time memory, which MAY stay. But for youngsters that use marijuhana heavily, it may be that it really blows their mind away. But they would be DEAD if they drank as much, so demonizing pot is really dumb. Being dead means no brain functions whatsoever, so instead of being less stellar in school, they would rot...
But: It seems like the dangers to young people were underestimated.