People living in cities run a higher risk of suffering from depression or an anxiety disorder.

Researchers now have a possible explanation: An experiment showed a much stronger response to stress in the brain of city residents.

Moving to the countryside sounds for many urban dwellers like relaxation, better air, less traffic noise and perhaps even time to work in your own garden. In fact, both, growing up and living in a city affects the brain’s ability to cope with stress. Researchers led by Florian Lederbogen from the Central Institute of Mental Health (ZI) in Mannheim elaborate in the science journal Nature on the connection between living in a city and mental stress.

Together with researchers from McGill University in Montreal, Canada, they observed in a series of several trials a total of nearly 160 volunteers solving particular tasks. Part of the volunteers were deliberately put under stress by the researchers: time to solve complicated mathematical problems was too short and the volunteers also had to put up with negative feedback through their headphones during the exercise. During the trial, researchers examined the brain activity of participants using magnetic resonance imaging.

In the city dwellers the so-called amygdala was more active than in people who live in rural areas. The amygdala area of  the brain becomes active during dangerous situations and is a kind of fear center. Changes in the amygdala have been linked with anxiety and depression. In people who lived in a big city with more than 100,000 inhabitants, the activity of the amygdala was  significantly higher than in those from towns with more than 10,000 but less than 100,000 inhabitants.

Among the participants, who had grown up in a big  city, the researchers observed a further difference: the so-called cingulate cortex – part of the frontal lobe of the brain – reacted more strongly. This in turn affects the amygdala. ‘These two regions in the brain are particularly susceptible to stress,” said Meyer-Lindenberg  of the research team.

City Dwellers suffer more frequently from depression, anxiety disorders, schizophrenia

A number of factors can in principal explain these observed differences, the researchers write in ‘Nature’: Environmental pollution, toxins, confinement, noise, and demographic factors that were not included in the study. The researchers, however, put forward the assumption that the altered brain activity is associated with social stress. 

It is already known that city dwellers have a higher risk of suffering from anxiety disorders – studies show that it is 21 percent above that of rural residents. The risk for depression or another mood disorder is even elevated by 39 percent. Having grown up in a city will also double the likelihood for schizophrenia, the researchers report.

Further studies should now show whether these results are transferable to other countries, as research was  primarily based on tests with German students.  The researchers suggest that city dwellers are primarily adversely affected because so many live  together in a confined space. ‘If we know the exact reason it can be considered in urban planning,’ said Meyer-Lindenberg. Cities are already home to more than half the world’s population –  and that percentage is rising.