Schizophrenia didn't exist as a concept until the early 20th century. There were various attempts to categories and label insanity in the late 19th, but before

Schizophrenia didn't exist as a concept until the early 20th century. There were various attempts to categories and label insanity in the late 19th, but before then people were either "mad", "not mad", or "occasionally mad" - perhaps with some sense of being religiously inspired in their madness. So it's impossible to say if schizophrenia is a modern environmental illness. FWIW I find it hard to imagine that modern life, even in cities, is more stressful than the life of a peasant in medieval Europe - someone who would be constantly torn between instinct and the threat of eternal agony in hell, and would also be terrorised by the very real threats of war, starvation, plague, and more mundane but still deadly illnesses. Not that modern homelessness and poverty, workplace aggression and bullying, relationship breakdowns, and the threat of physical violence aren't stressful in their own way. If there is an environmental component I'd guess it's at least as likely to be chemical as social. But maybe there's some difference in social stress types that everyone has missed.