City living can be tough on the brain — it's been linked to anxiety, depression and schizophrenia. By testing the brains of students raised or living in cities, researchers in Germany have located the brain areas linked to this stress reaction.

Previous studies have shown that city living during childhood is associated with a two- to three-fold greater chance of getting schizophrenia, and even after reaching adulthood, living in a city increases the risk for anxiety disorders by 21 percent and mood disorders by 39 percent compared with non-urban dwellers.

"If everyone was born in the country, there would be 30 percent fewer people with schizophrenia, which is a sizable reduction," said study researcher Andreas Meyer-Lindenberg, of the University of Heidelberg in Mannheim, Germany. "But, if everyone was born in the country, it would become crowded."

Big city living

To find out how city living may change the brain, the researchers scanned the brains of German students while they underwent social stress: The students were given math tests on an adaptive program that let them get only a third of the questions correct.

The program also indicated to each student that he or she had performed worse on the test than anyone who had taken it; meanwhile, the researchers pushed them to do better, telling them how important it was to perform well on the test.

During the stressful task, students who were living in cities showed increased activity in a brain region called the perigenual anterior cingulate cortex (PACC), while those who lived in cities in their early childhood (regardless of where they lived at present) showed increased activity in the amygdala. These increases were in comparison with non-city dwellers. [10 Things You Didn’t Know About the Brain]

"We were quite surprised it was that specific," Meyer-Lindenberg said. "Those two brain areas are separate but they are linked, they form a circuit."

Stressed brain regions

The amygdala and the perigenual anterior cingulate cortex together form a stress-response pathway in the brain, with the PACC regulating the amygdala, which then helps you process threats and temper your emotional reactions.

The researchers are looking next to see what parts of city living might influence this difference in brain activity, including factors like amount of green space available, type of neighborhood and culture of the region. These insights could help city planners build better, less anxiety-producing cities.

"We can't evade living in cities, and I'm not arguing we should," Meyer-Lindenberg told LiveScience. "But, what about the urban experience is it that influences our brains? If we find that, we can try to address it by city planning."

The study was published today in the journal Nature.

This article was reprinted with permission from LiveScience.

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