The history of the last two hundred years of humankind is the history of the city. In the world there are now more than 90 cities with populations in excess of 3 million people and 19 megacities with populations over 10 million. By contrast two thousand years ago, when the world population was approx 200 million, there were only 40 cities with more than 50 000 inhabitants. The population density of central London is now in excess of 10 000 people per square kilometre.
Their invention is relatively recent. Initially we, humans, lived our lives as hunter gatherers, living off nuts and berries with a population density a roomy one person per square kilometre. Then, seventy thousand years ago we began migrate from the African plains and ten thousand years ago nomadic societies began to give way to those which were settled and agricultural. These pastoralists were advantaged in that they could feed greater numbers of people and support a higher density of population. The downside was that their diet was less varied and that they were a sickly bunch, as with people now living in close proximity to their domesticated animals many diseases like influenza jumped the species barrier.
Cities have provided their inhabitants with an enormous number of benefits. There are improved opportunities for jobs, education, housing, and transportation. Universities have been founded and specialised health centres are possible. The breath of entertainments can satisfy every whim. Urban areas can also have much more diverse social communities allowing others to find people to whom they relate whom they might not be able to meet in rural areas. In fact it’s hard to imagine that many of the things we regard as everyday parts of modern life if people had not been able to live in the close proximity that city life makes a possibility.
But, the story of cities is not only the story of the people they serve ably. Life in a shanty town on the edges of a Sal Paulo or on a on the outskirts of Manchester sink estate is unlikely to offer any of these advantages. For many people, especially those in less developed countries, greater urbanization is likely to bring only poverty and disease. Even for people not so far down Maslow’s hierarchy, problems can abound as social bonds are often much looser and more fluid in cities than in smaller rural communities and rather than fit into those prexisting, city dwellers are forced to build their own social networks. Furthermore, modern social forces, mostly city based, have lead to an increasingly flexible employment market with more reliance on short term contracts and part time positions. This breeds uncertainty, stress, fuels competition and encourages us to see our colleagues as rivals and potential threats.
Thus, for almost anyone, cities place complex demands with concomitant stress. These circumstances appear to affect the proportion of the population suffering from mental illness. This urban settings effect is most acutely observed for schizophrenia, a disorder which occurs more commonly in cities. There are two competing hypotheses as to why this should be so. The ‘drift’ hypothesis suggests that urban environments attract selective migration of preschizophrenia individuals. On the other hand the ‘breeder’ hypothesis suggests that cities precipitate psychosis in genetically vulnerable people by the stress of social isolation and complex cognitive demands that characterise inner city life. Ultimately both are likely to contribute, and mental illness may be a cause or consequence of social isolation. A 2004 survey of all Swedes between ages 25 and 64 revealed that people living in the most densely populated had almost twice the rate of psychosis of those in the least populated areas.
Cities also tend be the home of migrants. In 2001 4.9 million people in the UK were born overseas, twice 2.1 million in 1951. Decade 1991 to 2001 saw the biggest leap in immigration to the UK – 1.1 million – since before the second world war. Migrants suffer the travails of city living, only more so; the upheaval of being uprooted from their homeland, having to cope with a strange new culture, learning a new language. Studies in London, Nottingham and Bristol found that schizophrenia is nine time as common in African Caribbean people and six times as prevalent in black Africans as in the white British population. Non migrant Afro-Carribeans and Africans do not have similar rates of illness; misdiagnosis by racist doctors has mostly been discounted as the cause for this difference. Soberingly the UN Global commission on international migration notes that:
Migrants are often viewed with suspicion by other members of society. In parts of the world certain politicians and media outlets have found it easy to mobilize support by means of populist and xenophobic campaigns that project systemically negative images of migrants…first generation migrants suffer disproportionately from physical, mental and reproductive health problems…they have lower educational attainments than nationals and generally live in poorer quality accommodation. Migrants also tend to occupy low-wage and low-status jobs and are more likely to suffer from long-term unemployment than other members of society (chapter 4)
Our species, homo sapiens, is thought to have originated 200 000 years ago. Full behavioural modernity, including language and music is thought to have emerged 50 000 years ago. Thus, compared to the age of our species, the city as a place to live is a relative new comer and it is perhaps small wonder that organise city living to everyone’s benefit, and that the project as a whole is still causing problems. The connection of mental illness to city dwelling suggests that we will be unable to fully address the problems of this problem until we have address wider issues of poverty.
An interesting fact (gleaned from a Robin Murray lecture): The incidence of schizophrenia in a particular area is predicted by the proportion of the population who vote in a General Election. The thinking is that If you live in an area where there is a sense of community and cohesiveness, then there is generally a higher percentage of people who vote, and lower incidences of schizophrenia. In a disorganised area, where nobody votes, and nobody knows their neighbours, there is lower ‘social capital’, and higher rates of schizophrenia. (see comment below for clarification on this)
Jared Diamond The rise and fall of the third chimpanzee is informative about hunter gatherers and is a generally excellent book
Paranoia: a 21st century disease is informative about urban living and its effect on mental health