CityReads | Does Big City Life Make People More Depressed?

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Does Big City Life Make People More Depressed?

The per capita prevalence of depression decreases systematically with city size.

Andrew J. Stier, Kathryn E. Schertz, Nak Won Rim, Carlos Cardenas-Iniguez, Benjamin B. Lahey, Luís M. A. Bettencourt, Marc G. Berman. Evidence and theory for lower rates of depression in larger US urban areas, Proceedings of the National Academy of Sciences Aug 2021, 118 (31).

Sources:

https://www.pnas.org/content/118/31/e2022472118

https://www.bloomberg.com/news/articles/2021-08-02/how-big-cities-help-fight-depression

Picture source: 

https://ephemeralnewyork.files.wordpress.com/2016/10/bentoncityactivitieswithdancehall.png

Living in cities changes the way we behave and think. Over a century ago, the social changes associated with massive urbanization in Europe and in the United States focused social scientists on the nexus between cities and mental life. Along with the urban public health crises of the time, a central question became whether cities are good or bad for mental health.

Social scientists have long studied the effects of cities on human wellbeing and happiness. The first American sociologists, Louis Wirth among them, were urban sociologists, similarly concerned with city characteristics, urban problems and happiness. Wirth's theory of urban life focused on how urbanism led to various negative consequences, including (1) cognitively, in terms of alienation, (2) behaviorally, in terms of deviance, and (3) structurally, in terms of anomie (normlessness), all of which would lead to unhappiness.

So do the empirical studies support the above theoretical view?

Subsequently, social psychologists started to document and measure the systematic behavioral adaptations among people living in cities. These adaptations included a more intense use of time [e.g., faster walking], a greater tolerance for diversity, and strategies to curb unwanted social interactions—such that people in larger cities act in colder and more callous ways. These studies attributed the influences of urban environments on mental health to the intensity of social life in larger cities, mediated by densely built spaces and associated dynamic and diverse socioeconomic interaction networks. They did not, however, ultimately clarify whether urban environments promote better or worse mental health. Consequently, concerns persisted that cities are mentally taxing  and can induce "stimulus overload", including stress, mental fatigue, and low levels of subjective well-being (SWB).

More recent studies have focused less on urban environments as a whole and more on contextual and environmental factors associated with depression. For example, a study of the entire population in Sweden uncovered a positive association between neighborhood population density and depression-related hospitalizations. In addition, individual factors of gender, age, socioeconomic status, and race, which vary at neighborhood levels within cities, have been found to be statistically associated with depression. Other studies using various measures of mental health and broader definitions of urban environments have found evidence for an association between poorer mental health in cities vs. rural areas.

However, this evidence and that linking SWB and cities have remained mixed and often explicitly inconsistent due to differences in 1) reporting (e.g., surveys vs. medical records); 2) types of measurement (e.g., surveys vs. interviews); 3) definitions of what constitutes urban; and 4) the mental disorders studied (e.g., schizophrenia vs. depression).

For these reasons, it is desirable to create a systematic framework that organizes this diverse body of research and interrogates how varying levels of urbanization influence mental health across different sets of indicators.

Mental health and city size

Examining scaling relationships of mental health outcomes with city size is a systematic way of investigating general urban effects on mental life, which places focus on collective influence on mental health disorders. The perspective of cities as interconnected networks that shape their inhabitants lives may also help to uncover environmental factors that influence other mental health disorders and overall well-being.

A recent paper published in the Proceedings of the National Academy of Sciences journal, Evidence and theory for lower rates of depression in larger US urban area, introduces a systematic framework for conceptualizing and modeling mental health in complex physical and social networks, producing testable predictions for environmental and social determinants of mental health also applicable to other psychopathologies.

This paper analyzed four datasets for depression rates across U.S. urban areas: the Substance Abuse and Mental Health Services Administration's National Survey on Drug Use and Health; the Centers for Disease Control and Prevention's Behavioral Risk Factor Surveillance System; and two Twitter datasets of individuals and their messages in an attempt to find "depressive symptoms". The researchers controlled for education, rate of population change, race, and income effects on depression rates for larger cities.

The study builds mathematical models around the prevalence of depression in U.S. cities based on the four databases and attempts to measure how city size and built environment affect the prevalence of depression. The results of the model analysis suggest that the per capita prevalence of depression systematically decreases with city size. The social interactions that large cities impose on their residents (even those that are cold or callous) help to mitigate the stresses that affect mental health.

The connection between observed systematic variations in socioeconomic networks and built environments with city size provides a link between urbanization and mental health. Many characteristics of cities have been recently found to vary predictably with city population size. These systematic variations in urban indicators are explained by denser built environments and their associated increases in the intensity of human interactions and resulting adaptive behaviors.

More specifically, people in larger cities have, on average, more socioeconomic connections mediating a greater variety of functions. This effect is understood theoretically by the statistical likelihood to interact with more people over space per unit time, leading to potential mental "overload" but also, to greater stimulation and choice along more dimensions of life. This expansion of socioeconomic networks is supported structurally by economies of scale (e.g., road length) in urban built environments and by occupational specialization and associated increases in economic productivity and exchange.

This effect leads to a number of quantitative predictions about the nature of urban spaces and socioeconomic variables, the most central of which is the variation of the average number of socioeconomic interactions, k (network degree), with city size, N. This result is important to mental health because depression is associated, at the individual level, with fewer social contacts . To translate the general scaling of social interactions with city size into a model for the incidence of depression in urban areas, we will now need to pay particular attention not only to the average number of social connections in a city of size N, k(N), but also, to its variance across individuals in that city and how they influence depression.

The risk of developing depression was sublinearly related to city size in the social network model. On average, large cities have more social interactions per capita. Individual risk of depression is inversely related to social connectedness. The combination of how cities shape social networks and how social networks shape individual depression risk results in a prediction of sublinear scaling of depression cases with increased city size (i.e., lower depression rates in larger cities).

We performed a logistic regression to assess how conditioning on race, income, education, and rate of population change (i.e., migration) impacted the observed decrease in depression rates for larger cities. We find general empirical support for the expectation that larger cities are associated with a decreased risk for depression even when conditioning on race, education, income, and migration.

This statistical relationship between depression and city size is consistent in larger cities across all four datasets and across a decade, despite the different ways in which depressive symptoms are measured and the different ways that the data were collected. Importantly, these results demonstrate that depression rates are substantially lower in larger US cities, contrary to previous expectations but precisely in line with our theoretical model and simulations.

Discussion and conclusion

Although the association between urbanization and mental health is foundational in the social sciences and in public health, it has remained challenging to characterize and assess quantitatively. This is particularly concerning as almost every nation worldwide continues to urbanize, with over 70% of the world's population expected to live in cities by 2050, and depressive disorders are already a leading global cause of disability and economic losses.

Based on size alone, large cities bear the brunt of the social and economic burden of depressive disorders. Our findings suggest that on a relative basis, however, smaller cities are actually worse off. The greater number of social connections in larger cities on the whole may provide a social buffer against negative affect and depression in the most vulnerable people (i.e., those with the smallest social networks). The alleged more callous and superficial social interactions in larger cities  may explain decreases in positive affect and SWB but simultaneously, may still buffer individuals from depression by decreasing negative affect (i.e., these more numerous social interactions may impact negative and positive affects differently).

The convergence of recent findings from urban science with evidence and theory from mental health studies offers a window for creating more systematic approaches to understanding mental health in cities. In this respect, the sublinear scaling of total depression cases with population size in larger US cities is a completely unexpected result characterizing the sociogeographic distribution of depression. While the results presented here speak only to larger urban areas in the United States, they suggest that larger city environments and urbanization can, on average, naturally provide greater social stimulation and connections that may buffer against depression. Although urban scaling theory has been shown to generalize across cultures and human history, it is critical for future work to examine whether the presented extension of urban scaling theory to depression generalizes to smaller cities and to other countries and cultures.

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