The research team then correlated the participants’ brain scan results with information they provided about where they currently lived or where they were raised. Activation of the amygdala increased in step with the population density of participants’ home towns: from rural areas to small cities to large urban settings.
The researchers think it is the social aspects of urban living — the stress of living and dealing with lots of people, and feeling more anxiety, fear and threat as a result — more so than other urban factors like pollution or noise that explains the higher stress-related brain responses among the city dwellers.