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City dwellers have a higher risk of depression
According to a recent study, the brain regions of urban people are measurably changed. This affects stress regulation, so that people in the city are at higher risk of developing mental illnesses such as depression or anxiety disorders. In addition, researchers from the Central Institute for Mental Health (ZI) in Mannheim identified an increased risk of schizophrenia.
Higher risk of fear and depression in big cities
In addition to an increased risk of accidents and heart attacks, life in the city also harbors the risk of developing mental illnesses such as depression or anxiety disorders. In relative terms, the risk of illness in the city is significantly higher than in rural regions. If children also grow up in large cities, the risk of developing schizophrenia is two to three times higher than in the country. Responsible for this context is a dysfunction in the brain regions of city dwellers who are responsible for the control and regulation of emotions and stress. For the first time, the scientific team led by Prof. Andreas Meyer-Lindenberg from the Central Institute for Mental Health (ZI) in Mannheim was able to publish concrete results in the research magazine "Nature". The research was done in collaboration with McGill University in Montreal.
Areas of the brain were examined by MRI
A total of 160 subjects from cities and rural areas took part in the study. All participants were examined using magnetic resonance imaging (MRI). The focus was on the brain areas of the amygdala. Brain activity was measured under stress and control conditions. To do this, the volunteers had to master difficult arithmetic tasks. In addition, they were practically insulted and subjected to harsh criticism. Thus, a stressful situation could be artificially created.
It was striking that the amygdala was significantly more active in the urban subjects than in the rural study participants. The named brain region is a so-called core area in the human brain that belongs to the Limbic system. In experiments, researchers have already been able to demonstrate that electrical impulses at different points in the amygdala can cause different reactions. Signals in the center led to tantrums or reactions to flight. At other points, vegetative situations could be provoked. For example, tachycardia (high heart rate, rapid heartbeat), craving to eat or a reproductive instinct could be triggered.
In urbanites, significantly stronger activities were measurable during the MRI, according to psychiatrist and doctor Prof. Meyer-Lindenberg. The subjects who grew up in large cities such as Hamburg or Berlin also reacted so-called cingular cortex (part of the frontal lobe of the brain) much more strongly than those who grew up in rural areas. "These two regions in the brain are particularly susceptible to stress," explains Meyer-Lindenberg.
The larger the place of residence, the greater the activity of the fear center
The typical parameters were measurable during the stressful situation. As a result, the pulse, blood pressure, and cortisol levels rose. This response was the same for all participants. However, the activity of the fear center was of value. The larger the place of residence of the participant, the more active the amygdala. When the subject grew up in a city, there were also increased frequencies of the perigenual anterior cingulate cortex (pACC). It was observed here that the connection between the amygdala and pACC worked much less well in the adult participants than in others. This observation is unique so far and could be helpful for neurological research. Because a disturbed brain circuit has been discussed as a risk factor for mental illnesses in the research world for several years. There could be an increased risk if certain neurological functions are changed.
The scientists were able to visualize the consequences in precise numbers. According to current studies, urban residents have an increased risk of depression of 39 percent. The bigger the city, the higher the risk of manifesting depression. The risk of developing an anxiety disorder was 21 percent higher. Anxiety disorders are an “unspecific fear without a specific reason”. In the acute case, patients experience a panic attack. This is accompanied by a racing heart, tremors, shortness of breath, excessive sweating, inner restlessness, dizziness and a feeling of derealization.
Exact causes must be researched
Subsequent studies will now examine exactly why city dwellers are so stressed. Most scientists assume that the increased noise level and the spatial confinement in which people live together are responsible. "If we know the exact reason, this can be taken into account when planning the city," emphasized the center director. Depression, stress-related illnesses such as burn out and anxiety disorders have been rising for some years. In contrast, more and more people live in cities. According to the latest analyzes, around half of all world inhabitants live in cities or large cities.
The Central Institute for Mental Health is a psychiatric clinic and research facility in Mannheim. In the "ZI" patient care and research and teaching in the field of mental disorders are linked. The foundation has a total of four clinic complexes. (sb)
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Image: Barbara Eckholdt, Pixelio.de