You know whose case is instructive and fascinating to me personally? The case of January Schofield, schizophrenic, Age 7. Its hard to argue that her case was induced by cultural/communicative factors since there is so much compelling evidence that she was born schizophrenic. From what I know about her case, she shows a very high IQ. But back to the context of the article, for me, its interesting to think about a schizophrenic like Jani with her childhood imagination but so enormously amplified and made real.
Jani's case still doesn't have me completely convinced. I also believe that she was born schizophrenic. I also believe that she, by way of her IQ, is a genius, which says something for the article in the OP (as well as what Victor claims about ideas of illness and genius). However, I'm not so sure that these unfiltered signals from whatever sources haven't had an effect. If communication, and I use the term in the systems theory sense, not necessarily language, didn't induce her schizophrenia, than I believe that it could have fostered it. Plus there is the added confusion caused by her intellect. One would assume that being able to learn at an accelerated pace (one of the articles says she was speaking grammatically correct sentences at 18 months), that not only was Jani viscerally "affected" by her environment, she also understood it to a great extent, though this may be masked by her schizophrenia. I do agree with your understanding that she probably has her imagination amplified, but imagination itself has at least some grounding in reality.
For example, and this is a shot in the dark, her imaginary friend "400", an orange tabby cat, corresponds to
"The Orange Cat" of Pasadena, which is close to UCLA where she began to receive treatment. Of course, this probably doesn't have any significance, but it is merely an example of what COULD have significance.
For an example of culture having an effect on and of schizophrenia, there is the example of
Nancy Scheper-Hughers study in Ireland. Admittedly, some of the cases were misdiagnoses, but that still doesn't account for the greater rate of schizophrenia in Ballybran. Also, this was a few decades ago, so it isn't the most current study. This thread has caused me to want to look into some more material concerning culture and schizophrenia, so I've just started looking at
a more current multidisciplinary approach spearheaded by anthropologist Janis Hunter Jenkins.
And as I said previously, there are different cases, and could be different causes from person to person.