title: Confirmation of synergy between urbanicity and familial liability in the causation of psychosis.
abstract: OBJECTIVE
  This study replicated a previous report that there may be substantial synergism between urbanicity (a proxy environmental risk factor) and familial clustering of psychotic disorder (a proxy genetic risk factor).
  
  
  METHODS
  The amount of synergism was estimated from the additive statistical interaction between urbanicity of place of birth and family history of schizophrenia or family history of any severe mental disorder in a population-based Danish cohort of 1,020,063 individuals.
  
  
  RESULTS
  There was significant interaction between urbanicity and family history; between 20% and 35% of individuals who had been exposed to both of these risk factors had schizophrenia possibly because of their synergistic effects.
  
  
  CONCLUSIONS
  The results suggest that a substantial proportion of the population morbidity force of schizophrenia may be the result of gene-environment interactions associated with urbanicity.
authors.affiliation: Maastricht University, P.O. Box 616, 6200 MD Maastricht, the Netherlands. j.vanos@sp.unimaas.nl
authors.forename: Jim
authors.initials: J
authors.lastname: van Os
authors.forename: Carsten B
authors.initials: CB
authors.lastname: Pedersen
authors.forename: Preben B
authors.initials: PB
authors.lastname: Mortensen
mesh_terms: D000328:Adult; D015984:Causality; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D003718:Denmark / Q000453:epidemiology; D005192:Family Health; D005260:Female; D005819:Genetic Markers; D020022:Genetic Predisposition to Disease; D006801:Humans; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D011618:Psychotic Disorders / Q000453:epidemiology* / Q000209:etiology; D012307:Risk Factors; D012559:Schizophrenia / Q000453:epidemiology / Q000209:etiology / Q000235:genetics*; D012931:Social Environment; D014505:Urban Population / Q000706:statistics & numerical data*
chemical_list: D005819:Genetic Markers