We’ve long known that city life takes its toll. As psychiatrist Andreas Meyer-Lindenberg writes in Scientific American Mind (March/April 2013), city dwellers are more likely to suffer from anxiety and depression. Further, anyone raised in a city is at much higher risk for schizophrenia, a disorder that devastates families and costs society billions in lost wages and lifelong medical care.

That’s quite a problem considering that our present is urban, and unavoidably, our future. More than half of the world’s population already lives in metropolitan areas. By 2050, it will probably be two-thirds.

Among the nongenetic suspects are lack of green space, too much noise, and pollution. But research by the Central Institute of Mental Health in Mannheim, Germany (where Meyer-Lindenberg is director), suggests that of all the urban stressors that tip our brains toward mental illness, social pressure—competition and weak community ties—is the worst. Most cities are of course rife with this pressure.

The short story on the research is that social pressure pushes certain parts of the brain into overdrive in ways that are very similar to what’s seen in people suffering from depression, anxiety, and schizophrenia. The same hyperactivity is also implicated in violent behavior.

Meyer-Lindenberg and his colleagues discovered this by subjecting students from cities, towns, and the countryside to verbal pressure while recording their brain activity. “We deliberately stressed them out,” he writes. And? “We could readily identify city residents by brain scan alone.” Their brains were far more sensitive to the pressure.

It appears that the longer someone lives in a city, the less communication there is beween the amgygdala, which modulates the “fight or flight” response and such emotions as fear, and a related region (the perigenual anterior cingulate cortex, or pACC, if you must know) that calms the amygdala. “Almost a third of schizophrenia cases might be avoided if more people were born in a rural setting,” Meyer-Lindenberg writes.

Obviously, we can’t all go back to the land. But there’s something that strengthens the stress-busting feedback loop between these two brain regions: friends, i.e. bonding. The volume of the amygdala actually increases with the size of your social circle (and I suspect that means friends, not Friends).

Yet another compelling reason to move fast on redesigning our cities and their institutions to promote community.

Scientific American Mind is available by subscription only. See Andreas Meyer-Lindenberg,“Big City Blues,” Scientific American Mind, March/April 2013, pp. 59-61.

Photo courtesy of  UNAMID via Creative Commons.