Pedersen & Mortensen (2001) found that individuals who spent their first 15 years of life in a highly urban area were nearly three times as likely to be diagnosed with schizophrenia, compared with people who grew up in rural areas
Mortensen et al (1999) investigated the effect of place and season of birth on risk of developing schizophrenia in a Danish cohort of 1.75 million. There was a clear dose-response relationship between urbanicity and risk of admission for schizophrenia.
In a classic research study by Faris and Dunham (1939), admission rates for schizophrenia in Chicago were demonstrated to be higher in inner city neighbourhoods than towards the periphery of the city.