Problem is, by the time I wasn't a teen, I wasn't that interested anymore. If you read the study, it's not saying much new--that for the vast majority of users it doesn't do much in the way of harm, but for some it can be quite harmful.
I haven't read the study, but the article linked here is simply wrong about the schizophrenia link. It says that there has been a marked increase in schizophrenia due to pot smoking, but if you look at teh history of schizophrenia diagnosis, you don't see a spike in the 60 and 70s when pot started to become widely used. This has been raised as an issue in studies past, and it's the reason that the most you can really say is that pot smoking as a teen may lead to early onset of schizophrenia that would have happened anyway.
Anyways, the truth is right in front of your eyes. The biggest threat to teen pot smokers is that they won't get off their lazy asses to work and will suffer from "Failure to launch."