I've done a lot of research on this topic. From the studies I've read, there seems to be a shift away from the idea that weed can cause psychosis in predisposed individuals and a shift towards the idea that people are may be predisposed to schizophrenia or who have schizophrenia are likely to smoke weed. There are definitely studies that show the that weed can bring out schizophrenia in people who are predisposed though.
It's causation vs. correlation. Many people who have schizophrenia are drawn towards weed. Also, there is debate about age correlation. Schizophrenia typically manifests itself in people around 19-30. Many people start smoking weed when they are 15, 16, or 17. Since we do not know whether someone who smokes weed and develops schizophrenia would have developed schizophrenia had they not smoked weed, it is difficult to determine if weed brings out latent schizophrenia. here's an article I found about this subject:
http://www.medicalnewstoday.com/articles/168519.php
From the article: "The study found it would be necessary to stop 2800 heavy cannabis users in young men and over 5000 heavy cannabis users in young women to prevent a single case of schizophrenia. Among light cannabis users, those numbers rise to over 10,000 young men and nearly 30,000 young women to prevent one case of schizophrenia."
While weed can trigger psychotic episodes, it does not permanently alter your brain chemistry unlike drugs such as benzodiazepines and alcohol. Which has lead some people to believe that it may not cause schizophrenia.
I'm not saying that weed use cannot cause or bring out latent schizophrenia. I am just trying to challenge ideas that are viewed as given. If we do not try to challenge our ideas and figure out the truth then we are not helping anything.
Schizophrenia is such a complicated mental disorder that it is difficult to perform accurate studies, especially surrounding weed.
The most important thing about this subject is to be reasonable. You can't say for sure that weed doesn't cause schizophrenia at all and you can't say for sure that it does.
I'd love to have an actual discussion on this topic or schizophrenia in general. My aunt had schizophrenia and is the reason I am so interested in it.