Since the 1960’s British clinicians have noticed that black migrants to the country, whether from the Caribbean or Africa itself, have a much higher rate of schizophrenia than the general population. It turns out that Indian and Pakistani immigrants also have higher rates.

Now part of the story is why these groups are so particularly affected, but the general lesson is that immigration increases everyone’s risk of going crazy; in fact it’s the largest environmental risk of factor. If the wrong person does it, changing countries can be disastrous.

The relationship between schiz and migration was first noticed in Norwegian immigrants to Minnesota (my people) by Odegaard in 1932. He found that most of his schizos had been considered eccentric even back in Norway and concluded that selective migration was the explanation.

This argument was taken by many psychiatrists, but it’s incorrect. After 1975, 1/3rd of the population of Suriname moved to the Netherlands and developed schizophrenia at 5x the rate of people left behind. That’s much too large an effect for selection. https://ajp.psychiatryonline.org/doi/full/10.1176/appi.ajp.159.4.669

It also interestingly turns out that immigrants to the Netherlands who live in neighborhoods where their own ethnicity is dominant have basically normal schiz rates, it’s those that go alone that are responsible for the excess https://ajp.psychiatryonline.org/doi/full/10.1176/appi.ajp.2007.07030423

People have a hard time accepting this finding and I don’t blame them. The experts were skeptical for a long time, too. Environmental effects aren’t normally so dramatic. It raises the question: how does that happen, exactly?

The preferred explanation is that it arises from “the long-term experience of social defeat, i.e., the chronic stressful experience of outsider status”. In other words, being a minority is bad, even worse than you appreciated.

Some people will find this comparison silly, but studies of primates and rats have found that introducing an intruder animal into a group of others creates dopaminergic hyperactivity in the brain: https://academic.oup.com/schizophreniabulletin/article/39/6/1180/1885614

The Amish have some of the lowest schizophrenia rates ever recorded, their only close competitors being tropical peoples with plenty of protective Vitamin D. Their isolation has cost them a lot, but in exchange they never have to worry about feeling like an outsider.

With the exception of a few wild men, most people need a home base. We don’t have to go as far as the Amish, but it would be nice if you didn’t need a complicated manual to understand how not to offend your neighbors.

And if you didn’t see it, here’s a long thread I wrote that touches on the association between skin color, Vitamin D, and schizophrenia risk: https://twitter.com/crimkadid/status/1270547158882832387