Humans are an urban species. At least 3.5 billion of us, more than 50% of the global population, lives in cities. That will hit 70% by 2050. Yet our early evolution never prepared us for living cheek-to-jowl in vast concrete settlements. This is precisely the way most of us will spend the 21st century, so the effect this has on our brains is important.
A study published in the journal Nature puts some hard data behind the question by testing how city living affects the way we cope with stress. Researchers scanned the brains of 32 healthy German volunteers from both rural areas and cities during a series of daunting math problems reinforced with negative comments. As it turns out, their brains behaved quite differently. Researchers observed higher activity in the amygdala–the brain region that assesses threats and memories of emotional events–among city dwellers compared to those living in towns or rural areas who exhibited progressively less activity. For those raised in cities, regardless of where they lived now, other areas of the brain regulating the amygdala also lit up (unlike the rural subjects) suggesting that conditioning can persist throughout life. No other brain structures showed significant deviations among the groups.
So is city living bad for you? It sure seems that way. The study speculates that “social defeat and chronic social stress” in cities affects the brain, but it does not try to answer so broad a question. As billions can attest, plenty of benefits go with moving to a big city. Urbanites are, on average, wealthier, eat healthier food, and receive better sanitation and health care compared to their countryside counterparts (although those benefits do not accrue proportionately to the urban poor). But not all is a walk in the (lovely city) park. We also know that living in cities increases the risk of developing anxiety and mood disorders–21% and 39% respectively according to a study published by Dutch researchers last year–as well as doubles the incidence of schizophrenia for those born and raised in urban areas.
But we’re only beginning to understand these psychological drawbacks. This new study presents the first compelling data to investigate about how urban environments rewire our brains for stress. As it turns out, New Yorkers may not be quite as tough as they thought. “The mind is a limited machine,” Marc Berman, a psychologist at the University of Michigan, told the Boston Globe during an interview about research into the cognitive drawbacks of urban living. “And we’re beginning to understand the different ways that a city can exceed those limitations.”