"There is growing consensus that cannabis use might increase the risk of developing schizophrenia. Our results support this, but also suggest that those at increased risk of schizophrenia may be more likely to try cannabis in the first place."
I've never found any good reason to suspect a link between use and cause in their data and the link between schizophrenia and use is almost always consistent with use of other drugs as well, and most any drug as far as that goes. For example, almost all of those who used marijuana also used alcohol and prescriptions drugs as well, but links to those (and combinations of them) are completely or mostly ignored in these studies.
Furthermore, they almost always suggest that "Paranoia" is one of the symptoms that Marijuana causes but they never address the fact that everyone they study has grown up with a lifetime of harsh disinformation and the very real threat of imprisonment for taking just a puff off a joint, which is a very good reason to get paranoid if you do.
As they say "Just because I'm paranoid doesn't mean they're not out to get me." and in this case "They" most certainly have been and still are in most places and everyone has seen it happen. The real result of that is, if you're not paranoid you're a idiot and most schizophrenics are not idiots. Some of them are geniuses. (https://www.psychologytoday.com/blog/beautiful-minds/200903/...)