Do we need to prepare ourselves for a more urbanised and, therefore, more depressed world? With the following article this article aims to stimulate a conversation between urban planning, architecture and neuroscience, in the hope of facilitating a more nuanced understanding of how urban and rural living conditions differentially impact upon our mental health. At a first glance, there are enormous methodological differences between the disciplines of urban planning and neuroscience. Nonetheless, considering the neuroscientific approach to the topic of cities is essential, as from it we can start to understand how city living affects inhabitants’ brain biology and could therefore influence the risk for developing mental disorders. On the bright side, there are also indicators that show a protective aspect of large cities with regards to mental health. Cities, therefore, may lend themselves to facilitating new and appropriate health intervention strategies.
Urban living is on the rise whereas rural living is becoming the exception – in all parts of the world and at an ever-increasing rate. The rapid pace of urbanisation is an important marker of the societal transition at large that has occurred over the past 30 years. Our world is shifting towards an urban, small-family or single household, and at the same time, an ageing society. In the next 30 years we will be faced with the growing challenges specific to our cities’ aged single urban populations.
But urban living is not only about getting older, it is also about getting stressed. Stress is the unspecific physiological and psychological reaction to perceived threats to our physical, psychological or social integrity. And urban living can be threatening if you haven’t enough space of your own, if you experience insufficient security or live under unstable economic conditions. Stress increases with the anticipation of adverse situations and the fear of not having the adequate resources to respond to them. From an evolutionary point of view, stress is the mechanism that prepares us for any ‘fight-or-flight’ reaction, and also causes us to evolve in order to better adapt to our environment. Although not harmful per se, stress may jeopardise our health when stress exposure is chronic or when complete recovery is not possible.
Living in an urban environment is long known to be a risk factor for psychiatric diseases such as major depression or schizophrenia. This is true even though infrastructure, socioeconomic conditions, nutrition and health care services are clearly better in cities than in rural areas. Higher stress exposure and higher stress vulnerability seem to play a crucial role. Social stress may be the most important factor for the increased risk of mental disorders in urban areas. It may be experienced as social evaluative threat, or as chronic social stress, both of which are likely to occur as a direct consequence of high population densities in cities. As for the impact on mental health, social stress seems to outweigh other urban stressors such as pollution or noise. Living in crowded areas is associated with increased social stress, since the environment becomes less controllable for the individual. Social disparities also become much more prominent in cities and can impose stress on the individual. Further, disturbance of chronobiological rhythmsis is more frequent in cities than in rural areas and has a negative influence on mental health and beyond. A recent meta-analysis showed that urban dwellers have a 20 per cent higher risk of developing anxiety disorders, and a 40 per cent higher risk of developing mood disorders. For schizophrenia, double the risk has been shown, with a ‘dose-response’ relationship for urban exposure and disease risk. Longitudinal studies on patients with schizophrenia indicate that it is urban living and upbringing per se, rather than other epidemiological variables, that increase the risk for mental disorders.
As urbanisation of our world is inevitable, we urgently need to improve our understanding of the threatening – as well as the health protective – factors of urban living. Evidence is beginning to surface that indicates that the urban population shows a stronger brain response to stress, and stronger cognitive impairment under stress. A recent fMRI study in the journal Nature, conducted by a German research group, showed that these effects seem to occur irrespective of age, gender, general health status, marital or income status. In this study, the amygdala (a brain region that regulates emotions such as anxiety and fear) showed higher activation under stress in healthy individuals from large cities compared to their counterparts from rural regions. Interestingly, activation grew with the size of the current home city. Further, activity in another brain region associated with depression, the perigenual anteriour cingular cortex, was positively correlated with the time that an individual had spent in a large city as a child. The more years someone had spent growing up under urban conditions, the more active this brain region tended to be.
The author of this piece, Mazda Adli is a Senior Physician in the field of Psychiatry and Psychotherapy at the Charité – Universitätsmedizin Berlin, Director of the Mood Disorders Research Group and Executive Director of the World Health Summit.
