For a kid who spent much of his childhood outdoors—alternately splitting time between the wooded park down the street, my friends’ backyards, and a patch of countryside my parent’s tended—I have been spending a lot of time in rather large cities as an adult. Ever since I left college, I’ve lived in cities that count their residents in hundreds of thousands and metro areas that count in the millions. It’s gotten me to wondering, what effect are these throngs of people having on my brain?

An answer to that question scrolled across my Twitter feed last week in the form of a paper published in Nature. “City living and urban upbringing affect neural social stress processing in humans.” Boom. The title alone seemed to say it all. But question answered? Not quite.

The paper is the first of its kind, merely lifting the corner of a page in what is likely to be a huge tome of neuroscientific discoveries on how urban life affects the development of our brains and how we react to the populous world around us. The study’s sample size is somewhat limited, but the results are statistical home runs. And like many pioneering studies, it raises many more questions than it answers.

The Germany-based researchers started by administering a difficult math test to 34 college students. While the students were taking the test, the researchers harangued them about their substandard score or slow progress to stimulate social stress. All the while, functional magnetic resonance imaging machines (fMRI) scanned the students’ brains, recording their activity. After the test and scans were completed, the researchers weighed the students’ patterns of brain activity against their place of upbringing—big city, small town, or rural area. Subjects who were raised in the city exhibited higher levels of activity in their amygdala, a region of the brain which processes emotion, and cingulate cortex, an area which regulates the amygdala. The results were so powerful that the scientists conducted a follow up experiment to be doubly certain. That study confirmed the findings of the first.

When analyzing the data, the researchers also differentiated between students who were living in the city versus those who actually grew up in the city. Somewhat disconcertingly, subjects who grew up in a big city had poor communication between the amygdala and cingulate cortex, something seen in people genetically predisposed to psychiatric disorders.

Together, these results suggested that students who had grown up in the city were more sensitized to stress. This should come as no surprise to anyone who has spent time in a city. Compared to the country, cities are chaotic, mile-a-minute places, filled with stressors and aggravations. Indeed, cities have a documented and profound effect on our mental well being, with greater prevalence of general mood disorders and anxiety along with rates of schizophrenia twice that of elsewhere.

This being a pioneering study, it’s findings are peppered with caveats. The sample size is small. The subjects were all German. Only students were tested, not a random sample from the population. No change was found in subjects’ cortisol levels, a marker hormone for stress—a curious result that will certainly be investigated further. But despite these qualifications, the study offers a preliminary confirmation of what many of us have long suspected—city living can get inside your head.

The questions the study leaves unanswered are myriad. Do different cities affect your brain in different ways? Certainly growing up in Cincinnati and Mumbai are two different experiences. And what about access to green space? Andreas Meyer-Lindenberg, the study’s main author, points out in an interview with Wired Science that, “You can go between city and country very quickly” in Germany, allowing city dwellers easy opportunities for respite from the stresses of urban life. And I would be remiss not to raise the issue of population density. It is, after all, this blog’s raison d’être. Fortunately, I should have something to report in the coming years. Meyer-Lindenberg and his colleagues plan to investigate density’s role in future studies.

Sources:

Lederbogen, F., Kirsch, P., Haddad, L., Streit, F., Tost, H., Schuch, P., Wüst, S., Pruessner, J., Rietschel, M., Deuschle, M., & Meyer-Lindenberg, A. (2011). City living and urban upbringing affect neural social stress processing in humans Nature, 474 (7352), 498-501 DOI: 10.1038/nature10190

Photo by Werner Kunz.

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