"Living in an urban environment during childhood or as an adult has consistently been found to increase the risk of schizophrenia by a factor of two."[0] While city life is as complex of a confounding factor as anything, the fact that they found hunter-gatherers have practically no incidence of SZR is interesting. Is the modern megalopolis simply too intense of a stimulus for the minds of the sensitive to handle without splitting into pieces?
[0] https://en.wikipedia.org/wiki/Schizophrenia#Environmental