Approximately half of the human population of the world today lives in urban settings. By the year 2050, 69% of all humans will live in cities. So, it is important to understand the physical and psychological health consequences of urban life. Already, many studies have been conducted on urbanization and mental health.It has been found that those who were born, raised and currently live in cities are at increased risk of psychological distress compared to those who are born and raised in urban settings. More specifically there is a 21% increase risk for anxiety disorders in urban dwellers compared to rural dwellers and a 39% increase risk of mood disorders in city dwellers. More shockingly, people born and raised in urban environments are twice as likely to develop schizophrenia than those born and raised in rural environments.
Urban social settings are considered a trigger for the above mental illnesses. The process through which these settings are internalized (and become problematic) is referred to as the social evaluative threat process. This cognitive thought process is comprised two components: social defeat and chronic social stress. Social defeat refers to the feeling of “losing” a confrontation, likely common in corporate office settings. Chronic social stress refers to the long-term experience of stress originating in social conditions. Interestingly, the physical brain events involved in this social evaluative threat process are largely unknown.The current study utilized functional magnetic reasoning imaging (fMRI) in three independent experiments to identify brain areas affected in healthy urban dwellers by acute social stress. These tests measure the brain activity in terms of blood flow: When certain areas are active, they “light up”.
Consistently, two distinct areas in the brain “lit up” more in urban dwellers than in rural dwellers: the amygdala and the pregenual ACC (pACC). The amygdala is responsible for signaling environmental threats and is highly involved in anxiety and depression. The amygdala was activated in participants who lived in urban settings regardless of where they were born. The pACC is involved in the sensation of emotion and is responsible for the storage of emotionally charged memories. This part of the brain also signals other brain structures during stress and is implicated in processing chronic social stressors such as social defeat. This area was activated particularly in individuals who were born and raised in urban environments regardless of whether or not they lived in cities in adult life. The link between these brain structures and mood and anxiety disorders have been well established. Furthermore, schizophrenia can be explained in terms of these active regions as well.
Schizophrenia has been linked to abnormalities in communication between these brain structures (pACC and amygdala) during the processing of negative stimuli. Interestingly, these abnormalities are seen in schizophrenic patients but not in individuals who are biologically at risk for developing the disease. This suggests the possibility of an environmental component- perhaps, urban living.
Overall, this study showed a relationship between activation of certain brain structures during social stress and urban living. Amygdala activity related to urban living suggests a susceptibility to mood and anxiety disorders that manifest in adult life. Activity of the pACC in individuals who spent their early life in urban settings may suggest a developmental component to mood and anxiety disorders that occur in adult life. Problems with communication between these two brain processes were especially relevant in schizophrenic patients who were twice as likely to have been born and raised and currently living in urban environments. This study opens the door for further research that many directly link mental illness with these brain structures under stressful circumstances. With this mental-health risk information, it may be possible to make changes to the social atmosphere in urban situations
Resource
Lederbogen, F., Kirsch, P., Haddad, L., Striet, F., Tosh, H., Schuch, P., Wust, S., Pruessner, JC., Rietschel, M., Deuchle, M., Meyer-Lindenberg, A. (2011). City living and urban upbringing affect neural social stress processing in humans. Nature, 474(7352) 498-501.