The 3.5-million number?
https://sardaa.org/resources/about-schizophrenia/
On assuming that marijuana use increases (as states legalize it), and is relative to the 3.5-million...my own assumption.
There’s not a disease advocacy organization in the country that doesn’t come up with wildly exaggerated stats in support of their raison d’etre.
Just look at the typically overreaching definition that the DSM offers for diagnosis on their front page.