Is there a citation for this? First time I've heard this said.
If that were true wouldn't all the ultra wealthy avoid living in cities at all?
I have no doubt there are vigorous academic arguments happening whether there are ways to mitigate the stress of population density and be healthier than would be expected. I'm open to that concept and ideas.
Yet the research on urban living and mental health is overwhelming - your chances of schizophrenia, mood disorders and anxiety skyrocket in cities. I was born in a large metro and lived on both coasts in huge urban areas, and I wish this weren't true because I like the energy of a city.
But you get a couple of whiskeys in me at dinner and I'll flat out say there's almost zero way to make a city healthy. People on top of each other, tremendous noise, light pollution and bad air quality leads to poor health for many people, as well as conflict.
(Although I rarely had a stress-free morning on the DC Metro)
Driving in rural areas or across the western US - piece of cake and even relaxing.
This is news to me.
I'm not saying your claim is wrong, just that this isn't sufficient. There is other evidence that shows that city living is healthier with longer lifespans and reduced obesity.
People in the city tend to be younger and higher income - both skew the numbers. Access to health services - advantage city vs rural. But the stress level is off the charts higher in a city. This is terrible for you.
There is some evidence that suburban or exurban might be the sweet spot, where you get the benefit of access to care and less daily stress.
Walking and movement is important too, so if you can combine income with small town living (community) in an active way you may be way ahead of the game.