Imagine that you are lying down having an fMRI scan, inside a noisy, airtight machine that is usually quite unnerving. As if that were not enough, you have to solve some pretty complicated math problems against the clock.
You are trying hard, but the researchers are not satisfied and ask you to concentrate more, to respond faster. As if that were not enough, every time you make a mistake they tell you that you did something terrible, destroying your self-esteem and getting on your nerves.
That was the scenario created by researchers from the University of Heidelberg. The objective was to generate a highly stressful situation in these people, to see how their brains responded. And they discovered that the brains of people who lived in the city did not deal very well with emotional stress.
“Urban” brains don’t know how to manage stress
These neuroscientists were interested in two specific regions of the brain: the amygdala and the pregenual anterior cingulate cortex. The amygdala plays an essential role in evaluating threats that come from the environment and the appearance of the fear response, being the main responsible for emitting the alarm signal at the brain level when something is wrong.
On the other hand, the pregenual anterior cingulate cortex is involved in the autonomic and emotional response to meaningful stimuli, an area that, by the way, is damaged in people who suffer from bipolar disorder. Basically, it is involved in emotional sensations and their autonomous expressions.
The researchers noted that the level of reactivity of the amygdala depended on the size of the city. That is, people who lived in large cities had a more active amygdala than those who lived in smaller cities and these, in turn, showed a higher level of activation than those who lived in rural areas. This means that the amygdala reacted more by triggering a stress response to a greater number of situations in urban people.
However, the discoveries did not end there. These researchers also found that the activity of the pregenual anterior cingulate cortex depended not only on where people lived but also on where they grew up. Those raised in a rural environment had a less active pregenual anterior cingulate cortex. What does that mean? That they could better control emotional expression.
In contrast, those who were born and raised in urban environments had a more active pregenual anterior cingulate cortex. Another study conducted at the University of New Mexico suggested that this area of the brain appears to be responsible for maintaining the conflict mechanism. In other words, it keeps the focus of tension active, which would prevent us from turning the page, keeping us in a state of hypervigilance and permanent anxiety.
In fact, it is no coincidence that previous studies have found that being born in a city increases the risk of suffering from schizophrenia. A group of researchers from the University of Amsterdam found that living in a city doubles the risk of developing schizophrenia. As if that were not enough, it has been found that urban living increases the risk of suffering from anxiety and mood disorders by 21% and 39%, respectively.
Why do cities affect our mental balance so much?
Urban life plunges us into a paradox: loneliness in the crowd. We are surrounded by people, but we maintain fragile connections, so many people feel deeply alone. And unchosen loneliness is often a precursor to mental disorders.
These neuroscientists think that our brains are not designed to live in urban environments as large as those we currently have, but rather in smaller nuclei in which we can establish meaningful human relationships that allow us to build a solid support network that sustains us in difficult times.
If we already have a predisposition, the tension of urban life and the fragility of its bonds can act as triggers for psychological disorders. In other words, the stress in the city and its ways of life aggravate emotional problems.
On the other hand, a group of researchers from Hammersmith Hospital in London point to dopamine. It is a neurotransmitter that performs different functions, one of which is to tell us that something important is happening – whether good or bad. Interestingly, many people with schizophrenia also have very high levels of dopamine.
These neuroscientists believe that cities increase our dopamine levels because we are continually bombarded with stimuli that put us on alert, from car horns to the agitation that always hovers in the environment. This sustained stress – combined with loneliness – could prevent our brain from relaxing, keeps the amygdala active, as if we were living in a situation of permanent danger, and becomes a time bomb for our mental health that can explode at any moment.
Sources:
Wilcox, C., Pommy, J. & Adino, B. (2016) Neural Circuitry of Impaired Emotion Regulation in Substance Use Disorders. American Journal of Psychiatry ;173(4): 344-361.
Tost, H., Champagne, FA & Meyer, A. (2015) Environmental influence in the brain, human well-being and mental health. Nature Neuroscience ; 18: 1421–1431.
Peen, J. et. Al. (2010) The current status of urban-rural differences in psychiatric disorders. Acta Psychiatr Scand ; 121: 84–93.
Drevets, W. C. et. Al. (1997) Subgenual prefrontal cortex abnormalities in mood disorders. nature ; 386: 824 – 827.
Lewis, G. (1992) Schizophrenia and city life. Lancet ; 340(8812):137-140.
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