From the Editor
Do cities make us sick?
It’s a question people have been asking for years with many advocating that we should – to steal a line from Huckleberry Finn – get the lights fantastic out of town.
This week, we look at a new paper just published in The Canadian Journal of Psychiatry that looks at urban vs. rural populations and depression.
Then, turning to The Atlantic, we consider an essay written by a psychologist that looks at the connection between psychosis and cities.
Thoughts on Cities and Depression
“The Prevalence of Major Depressive Episodes Is Higher in Urban Regions of Canada”
Kathryn Wiens, Jeanne V. A. Williams, Dina H. Lavorato, Andrew G. M. Bulloch, and Scott B. Patten
The Canadian Journal of Psychiatry, 12 July 2016 Online First
Major depressive disorder is a substantial contributor to the global burden of disease, estimated to affect approximately 350 million people worldwide. There has been speculation that urban living may contribute to an increased frequency of mental disorders. However, current literature is inconsistent, with some studies finding no difference, with some reporting higher prevalence in rural compared to urban or vice versa. Recently, a national US study indicated no difference, a finding that is not consistent with results from other countries. In Canada, an analysis of cross-sectional data from the 1998 longitudinal National Population Health Survey (NPHS) found equivocal results. No overall association was found, but a trend (P = 0.05) was observed when the analysis was restricted to nonimmigrant populations. An analysis of data from the 2002 Canadian Community Health Survey, Mental Health and Wellbeing also found ambiguous results for major depression (P = 0.06).
There are several likely explanations for this inconsistency. If an existing association is weak, individual surveys lack the sample size (and power) to detect it. Alternatively, an association may not exist, or there may be international differences in the definition of urban and rural status or assessment of MDE. Using meta-analysis techniques, our goal was to decisively determine whether an association exists in Canada and to quantify the strength of any association that may exist.
So opens a Brief Communication by Kathryn Wiens et al. that considers an old question: is depression more common for people living in cities? Though we assume the answer is yes, Wiens and her co-authors note the lack of conclusive study in the area.
Here what they did:
· They drew data from Statistics Canada’s Canadian Community Health Survey (CCHS), done between 2000 and 2012. In each CCHS, Stats Canada conducted a nationally representative survey of Canadian households, interviewing one representative in selected homes (age 15 or older). As well, two mental health surveys from 2002 and 2012 were used.
· Past year depression (MDE) was assessed using a CIDI in the mental health survey and an abbreviated form in the CCHS.
· Urban and rural areas were defined as follows: “Statistics Canada defines urban and rural status based on population density and proximity to a census metropolitan area (CMA) or census agglomeration (CA). Urban regions contain a population of at least 1000 with no fewer than 400 persons per square kilometre and can be further subcategorized into urban core, urban fringe, and urban outside CMA/CA. Urban cores are the regions with at least 10,000 individuals, located inside a CMA or a CA. Urban fringe includes all population centers within a CMA/CA that inhabit fewer than 10,000 people, and urban outside CMAs/CAs are the regions with 1000 to 9999 individuals not residing within a CMA/CA.”
· Statistical analyses were done.
Here what they found:
· In total, 9 census surveys were used, with a combined sample size of 477,449.
· Pulling together the survey-specific log odds ratio (OR) estimates for major depressive episode (MDE) in urban compared to rural regions:
· “The pooled estimate… translates into an odds ratio of 1.18… which demonstrates a statistically significant (P < 0.01) higher prevalence of MDE in urban compared to rural regions…”
· “While urban fringe regions demonstrate the highest odds of MDE… this is very similar to the estimates for urban core… or urban outside CMA/CA regions… These results support the decision to combine the urban subcategories into one urban region when assessing the urban-rural differences in prevalence.”
· “The association between urban status and MDE was highest in Newfoundland… and lowest in British Colombia…”
The main finding of this research is that odds of MDE are 18% higher for individuals living in urban compared to rural regions of Canada. This supports the idea that previous studies have lacked sufficient power to detect such a difference. While the data sets analyzed in prior Canadian studies were large (14,781 in the 1998 NPHS analysis and 31,321 in the 2002 CCHS analysis), these studies may nevertheless have lacked power to detect a weak effect.
A few thoughts:
1. This is a good paper.
2. It’s interesting that the authors, using Canadian census data, were able to draw a conclusion that other studies couldn’t. It’s elegant work.
3. And, of course, it’s not the only work drawn from this data. Earlier this year, you will recall that Patten et al. did a great paper looking at the percentage of Canadians receiving “potentially adequate care” for their depression (concluding that only about of half of Canadians do).
4. Of course, the larger questions about cities and mental illness remain: Do cities attract people with depression? Or are the stresses and environmental exposures of urban life more likely to result in depression? And does the trend hold for other mental illnesses?
5. For a consideration of psychosis, see below.
Thoughts on Cities and Psychosis
“The Mystery of Urban Psychosis”
The Atlantic, 15 July 2016
Southwyck House in South London is a block of flats so intimidating that it is often mistaken for a prison. Locally known as the Brixton ‘barrier block,’ it has a stark exterior of brick and concrete that literally looms over you, giving the impression that unseen people are staring down through the sparse rectangular windows.
It was built as a social housing project, designed to shield its residents from the noise of a phantom motorway that was intended to run from Blackheath to Battersea. The road was never built due to petty political squabbles, but the building now stands as a seven-story barricade against its illusory traffic.
If you’re not used to the built-up environment of the inner city, the block can certainly feel unsettling. But here, urban alienation may run deeper than mere architecture. The area was found to have the highest rate of diagnosed schizophrenia in a large study of South London, even when compared with directly adjacent neighborhoods.
So opens an essay by psychologist and writer Vaughan Bell.
Bell summarizes the literature well:
· “The link between psychosis and city living was first noticed by American psychiatrists in the early 1900s who found that asylum patients were more likely to come from built-up areas.”
· Over the last quarter century, systematic and statistically controlled studies have reaffirmed the association between psychosis and cities.
· In a major Danish study using health records, “the risk of being diagnosed with schizophrenia increased in a small but proportional way as people spent more time spent living in urban environments.”
Bell notes: “To many, this provides evidence that cities are universally bad for our mental health—something that chimes with a strong cultural belief that associates the natural world with tranquility.”
But is it just possible that people with schizophrenia end up living in cities (and poverty). Bell notes the “social drift” hypothesis, before discussing the possible role of genetics. If there are many possible explanations, then, there doesn’t seem to be one clear explanation. The piece closes with Bell observing that researchers are taking a more multidisciplinary approach.
My final thought: after a century of study and observation, like in so many areas of psychiatry, we don’t have a clear understanding of what’s going on and why – a reason to love and hate our young field at the same time.
And, of course, for all of us to read more…
Reading of the Week. Every week I pick articles and papers from the world of Psychiatry.