City life increases stress susceptibility

The risk of mental illness among citizens is significantly increased

23/06/2011

City life causes increased susceptibility to stress. Numerous studies have found in the past an increased incidence of depression and anxiety disorders in the population in the major cities. Researchers at the Mannheim Central Institute of Mental Health have now found that activity in two brain regions responsible for processing stress and emotions is significantly different among city dwellers and rural dwellers.

People living in a big city with more than 100,000 inhabitants are much more susceptible to social stress than people living in rural areas, according to Florian Lederbogen of the Mannheim Central Institute of Mental Health and colleagues in the latest issue of the journal „Nature“. In investigating activity in the various brain areas during a stressful situation, city dwellers in the amygdala as well as in the region of the perigenual anterior cingulate (pACC) showed significantly higher activity than rural dwellers, according to the current study. Since both brain regions are responsible for the processing of emotions and stress, the results of the investigation also allow conclusions to be drawn on the susceptibility of the urban population to stress, explained Florian Lederbogen and colleagues.

Increased brain activity of the urbanites in the stress test
In order to take a closer look at the increased susceptibility of urbanites to stress, the team of psychiatrists and psychologists has published 32 so-called volunteer healthy volunteers in the so-called Montréal Imaging Stress Test.„dung“-Test), in which the brain activity of the study participants during a stress situation was recorded with the help of a functional magnetic resonance tomograph (fMRI). The subjects had to solve time-consuming heavy computing tasks and were exposed at the same time over headphones critical comments of the scientists. As a result, brain activity in all stressors and emotions-processing regions of the amygdala and perigenular anterior cingulum (pACC) is increased in all subjects. However, in experimental subjects, who currently live in a city with more than 100,000 inhabitants, brain activity was significantly higher in the amygdala than in the rural inhabitants, reports Florian Lederbogen and colleagues. This result has also been confirmed in the context of a subsequent check-up, the researchers continue. In addition to the altered brain activities were also normal stress reactions such as high blood pressure and an increased release of the stress hormone cortisol observed.

Growing up in the city increases the susceptibility to stress
In addition to the significantly increased brain activity of the amygdala in people who currently live in a large city, the researchers of the Mannheim Central Institute of Mental Health also found a long-term effect of city life. Florian Lederbogen and colleagues interviewed the study participants according to their previous places of residence and then multiplied the population of the home towns with the years spent there to develop an individual indicator for the urban or rural life of the subjects. The higher the ratio, the more urban the past life of the participants in the study was, said the scientists of the Mannheim Central Institute of Mental Health. In comparing the individual measures with the brain activity of the subjects, the researchers found that as the value of the indicator increased, activity in the area of ​​the pACC also increased significantly during the stress test. Since the region of the pACC makes a significant contribution to the control of the activity of the almond kernel and a good interaction of the two brain regions is crucial for the processing of stress and emotions, Florian Lederbogen and colleagues assume that in the changed sphere of action or the worse interaction of Mandelkern and pACC also explains the increased susceptibility of urbanites to stress. Previous studies have already provided evidence for a link between the disturbed interplay between the two brain areas of amygdala and pACC with reduced mental stability, Lederbogen and colleagues said.

Further investigate the stress processing of rural and urban residents
Although current research suggests that „the further man moves away from his natural biotope, the higher the price will be“ However, the study of the Mannheim researchers could provide no clear scientific evidence that the size of the place of residence directly influences the stress processing, commented the biopsychologist Peter Walschburger of the Free University of Berlin the current article in the journal „Nature“. The number of study participants is too low and the data refer exclusively to Germany, which makes an international comparison much more difficult, said Walschburger. In order to achieve reliable results, therefore, a long-term study with significantly more participants and taking into account different living conditions in the different cities is necessary. For the starting conditions vary greatly from city to city and Walschburger emphasized that he could hardly imagine that there was no difference between the effects of living in the center of Mexico City and living in an eco-settlement on the outskirts of Freiburg. It must also be taken into account whether someone lives voluntarily in a large city or whether the job or the study requires it. „Such factors would have to“ in further studies „be urgently involved“, emphasized biopsychologist Peter Walschburger.

Urban population generally more susceptible to mental illness
Overall, the results of the researchers of the Mannheim Central Institute of Mental Health are particularly interesting in view of the statements of older comprehensive studies, as they have already found a significantly increased susceptibility of the urban population to mental illness. To be sure, the current study by Florian Lederbogen and colleagues does not provide any clear scientific evidence on the impact of urban life on the risk of mental illness. However, the observed increased activity in the brain regions of the amygdala and the pACC among the city dwellers offers a possible explanation for the increased mental instability of the urban population already proven in previous studies. It is known that city dwellers are about 20 percent more likely to be affected by anxiety disorders and people who grew up in the city, compared to the people around twice as often suffer from schizophrenia, said Peter Walschburger. On the other hand, there are other studies that show lower suicide rates among urban populations than rural populations in some countries, comment Daniel Kennedy and Ralph Adolphs of the California Institute of Technology in Pasadena „Nature“ Items. Overall, the current study, however, the evidence suggests that a growing up and living in the city significantly affects the processing of social stress in the brain, so the conclusion of Florian Lederbogen and colleagues. (Fp)

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