Recently we’ve been reading and discussing The Eden Express, Mark Vonnegut’s account of his personal experience with schizophrenia. For our discussions we’ve had to do quite a bit of research on schizophrenia and one of the things that greatly interested me were some of the risk factors that made people more likely to present with the disorder. One risk factor that was particularly interesting was urbanization. Studies showed that children whose mother’s lived in urbanized areas while they were in utero were at a greater risk for schizophrenia than those whose mother’s had been in more rural environments throughout their pregnancies. It made me wonder what other disorders could be linked to urbanization.
Through research I found an article published on the subject of urbanicity and ASD, Autism Spectrum Disorders. ASD are much like schizophrenia in that the risk factors range from genetic mutations to environmental components. A group of researchers in Denmark looked at all children born in Denmark between January 1993 and December 2005. They calculated the incidence rate ratios of ASD for various areas across Denmark that differed in their levels of urbanization. Urbanization was broken up into five levels, capital, capital suburb, provincial city, provincial town, and rural area, based on population density per square mile. For each subject with in those areas they then took into account factors such as maternal age, paternal age, gestational age at birth, sex, birth weight, and parental psychiatric history.
Using statistical analyses they found that in the capital, the place with the highest urbanization, the cumulative incidence of ASD for male children was 17.7 out of every 1000 while in rural areas the incidence was 8.1 for every 1000. The incidence for capital suburbs, provincial cities, and provincial towns were 13.9, 10.8, and 9.7 respectively. The cumulative incidence among female children pointed in the same direction with the incident rate being highest in the capital and lowest in rural areas, with the other three falling in between. Overall the study showed that ASD, like schizophrenia, can be positively associated with the place of residence at birth.
So is urbanization a bad thing? Why would urbanization increase the risk for disorders like schizophrenia and ASD? Since we don’t have comprehensive or definitive answers it kind of makes me glad that I’m from a small town that’s located in the middle of nowhere.
Lauritsen, Marlene B., Aske Astrup, Carsten Bøcker Pedersen, Carsten Obel, Diana E. Schendel, Laura Schieve, Marshalyn Yeargin-Allsopp, and Erik T. Parner. “Urbanicity and Autism Spectrum Disorders.” Journal of Autism and Developmental Disorders 44.2 (2014): 394-404. Print.
On Psychology and Neuroscience 
I have often heard these findings used to make an argument for air pollution as a possible cause of ASD. When I first heard these claims I dismissed pollution as being an unlikely sole “cause” of ASD, but a recent article I read that discusses research by Harvard University suggests that this link has been somewhat made! Here is the link for anyone who is interested: http://www.heraldextra.com/news/local/harvard-draws-link-between-autism-and-air-pollution/article_53b6a81e-91ac-58f8-8556-70e6eac70cd1.html. I’m still not sure if I’m a believer of the air pollution ASD theory, but the evidence is interesting between this study and the one you discussed above. I wonder if the two-hit hypothesis that can be applied to schizophrenia could also be applied to ASD. Most likely, environmental toxins alone could not be considered a “cause” of either disease, but perhaps they may a contributing factor. Interesting stuff to think about, especially since this is really hot research right now.
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