That article uses psychosis and schizophrenia interchangeably. There's also no mention of the familial nature of schizophrenia. There's a genetic link in many cases and there's been work in that area that's starting to identify particular genes that are associated with the disorder.

It could be that infection with T. gondii is sometimes the difference between simply having a predisposition towards schizophrenia and actually developing the symptoms. Pot use in the late teens and early 20s can have the same effect. It doesn't cause schizophrenia, but it may be a trigger than leads a genetically predisposed individual to develop the disorder.