• G Lewis, A David, S Andréasson, and P Allebeck.
• Section of Epidemiology and General Practice, Institute of Psychiatry, Denmark Hill, London, UK.
• Lancet. 1992 Jul 18; 340 (8812): 137-40.

AbstractPrevalence of schizophrenia and rates of first admission to hospital for this disorder are higher in most modern industrialised cities, and in urban compared with rural areas. The "geographical drift" hypothesis (ie, most schizophrenics tend to drift into city areas because of their illness or its prodrome) has remained largely unchallenged. We have investigated the association between place of upbringing and the incidence of schizophrenia with data from a cohort of 49,191 male Swedish conscripts linked to the Swedish National Register of Psychiatric Care. The incidence of schizophrenia was 1.65 times higher (95% confidence interval 1.19-2.28) among men brought up in cities than in those who had had a rural upbringing. The association persisted despite adjustment for other factors associated with city life such as cannabis use, parental divorce, and family history of psychiatric disorder. This finding cannot be explained by the widely held notion that people with schizophrenia drift into cities at the beginning of their illness. We conclude that undetermined environmental factors found in cities increase the risk of schizophrenia.

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