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It's estimated that by the year 2050, 69% of all humans will live in urban areas. Although city dwellers, on average, are wealthier and have better access to healthcare and other services, there are some downsides to urban living. For instance, people raised in cities are more prone to mental disorders than people who live in rural areas. This is actually not a new news. For some time now scientists have known about the link between city living and mental illness. But, how exactly city living affects the brain has been relatively uncharted territory...until now.
New research published a few weeks ago in the journal Nature shows that the brains of city and country folk respond differently to stress. Specifically, when put in a stressful situation, those who either grew up in the city or currently reside in heavily populated areas showed increased activation in areas of the brain responsible for processing negative emotions relative to folks in less populated areas.
To show how one's living environment influences the brain, neuroscientists at the University of Heidelberg in Germany used functional magnetic resonance imaging (fMRI) to scan the brains of volunteers while they performed a series of math problems under time pressure. The math problems were difficult by design - people averaged only between 25% and 40% correct. And, while they did the problems, people got negative feedback via headphones that they were doing poorly.
The entire procedure was designed to create a form of social stress. And, indeed, it did. Volunteers showed increases in the stress hormone cortisol compared to a control condition in which there was not pressure to succeed. A hormone produced by the adrenal gland, cortisol is secreted at higher levels when people are in stressful situations. Because of this, cortisol is often referred to as the "stress hormone."
In addition to overall increases in cortisol, the stressful math situation activated several different brain areas, two of which specifically related to people's history of urban living. Currently living in a city was related to increased activation in the amygdala during the stressful math task. As I have blogged about before, the amygdala is an almond shaped region deep in the brain that is a major player in our emotional responses. Increased amygdala activity often coincides with unpleasant emotional reactions. And, the cingulate cortex, which helps to regulate the amygdala and processes negative emotions, was more active during the stressful task for people who were brought up in densely populated areas as compared to those who grew up in rural environments.
So, yes, city living does have its benefits. But, it also seems to increase our sensitivity to social stress. Given that an urban lifestyle is inescapable for many of us, understanding how exactly city living affects the brain is an important first step in determining how to get the best out of an urban lifestyle while avoiding the negative mental side effects that may come along with it.
For more on how stress impacts brain functioning, check out my book Choke!
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Lederbogen, F. (2011). City living and urban upbringing affect neural social stress processing in humans. Nature.
