American Journal of Epidemiology Advance Access originally published online on May 4, 2006
American Journal of Epidemiology 2006 163(11):971-978; doi:10.1093/aje/kwj169
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Original Contribution |
Are the Cause(s) Responsible for Urban-Rural Differences in Schizophrenia Risk Rooted in Families or in Individuals?
From the National Centre for Register-based Research, University of Aarhus, Aarhus, Denmark
Reprint requests to Carsten B. Pedersen, National Centre for Register-based Research, University of Aarhus, Taasingegade 1, 8000 Aarhus C, Denmark (e-mail: cbp{at}ncrr.dk).
Many studies have identified urban-rural differences in schizophrenia risk. Hypothetical underlying cause(s) may include toxic exposures, diet, infections, and selective migration. The authors investigated whether the underlying cause(s) responsible for the urban-rural differences were rooted in families or in individuals. Linking data from the Danish Civil Registration System and the Danish Psychiatric Central Register, a population-based cohort of 711,897 people aged 15 years or more was established. Overall, 2,720 persons developed schizophrenia during the period 1970–2001. The authors evaluated whether the nearest older sibling's place of birth had an independent effect on schizophrenia risk. If the cause(s) responsible for the urban-rural differences are rooted in individuals only, the nearest older sibling's place of birth should have no independent effect. In this analysis, the nearest older sibling's place of birth had an independent effect; among persons who lived in a rural area during their first 15 years of life, the relative risk was 1.59 (95% confidence interval: 1.10, 2.30) if their nearest older sibling had been born in the capital area as compared with a rural area. Some of the cause(s) responsible for the urban-rural differences in schizophrenia risk are rooted in families, but some might also be rooted in individuals.
cities; environment; family characteristics; genes; risk factors; schizophrenia; siblings; urbanization
Abbreviations: CI, confidence interval; CRS, Civil Registration System; ICD, International Classification of Diseases
Editor's note: An invited commentary on this article appears on page 979.
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 D. March and E. Susser Invited Commentary: Taking the Search for Causes of Schizophrenia to a Different Level Am. J. Epidemiol., June 1, 2006; 163(11): 979 - 981. [Abstract] [Full Text] [PDF]
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