title: Somatic diseases and conditions before the first diagnosis of schizophrenia: a nationwide population-based cohort study in more than 900 000 individuals.
abstract: OBJECTIVE
  Schizophrenia is associated with excess physical comorbidity. Yet, to our knowledge, large studies are lacking on the associations with somatic diseases before the onset of schizophrenia. The authors conducted a nationwide study of the full spectrum of treated somatic diseases before the first diagnosis of schizophrenia.
  
  
  METHODS
  Nationwide sample of the Danish population consisting of singletons (n = 954351) born 1977-1993 and followed from birth to 2009, during which period 4371 developed schizophrenia. Somatic diagnoses at all general hospital contacts (admitted or outpatient care at a somatic hospital) from 1977 to 2009 were used as exposures. The incidence rate ratio (IRR) of schizophrenia was calculated using Poisson regression adjusted for confounders.
  
  
  RESULTS
  Among the 4371 persons who developed schizophrenia from 1992 to 2009, a total of 4180 (95.6%) persons had a previous somatic hospital contact. A history of any somatic hospital contact was associated with an elevated risk of schizophrenia (IRR = 2.04, 95% CI = 1.77-2.37). A wide range of somatic diseases and conditions were associated with an increased risk of schizophrenia, including epilepsy (IRR = 2.26, 95% CI = 1.93-2.62), nutritional or metabolic disorders (IRR = 1.57, 95% CI = 1.39-1.77), circulatory system diseases (IRR = 1.63, 95% CI= 1.38-1.92), and brain injury (IRR = 1.58, 95% CI = 1.45-1.72).
  
  
  CONCLUSIONS
  A wide range of potential etiological factors could have contributed to the observed associations, including genetic or physiological overlaps between conditions, and interacting immunological, behavioral, and neurodevelopmental factors.
authors: Mental Health Centre, Capital Region of Denmark, Copenhagen University Hospital Bispebjerg, Bispebjerg Bakke 23, 2400 NV, Copenhagen, Denmark; The Lundbeck Foundation Initiative for Integrative Psychiatric Research, iPSYCH, Aarhus University, Fuglesangs Allé 4, Aarhus V, Denmark holger.jelling.soerensen@regionh.dk.
authors: Holger J
authors: HJ
authors: Sørensen
authors: National Centre for Register-Based Research, Aarhus University, Fuglesangs Allé 4, Aarhus V, Denmark; The Lundbeck Foundation Initiative for Integrative Psychiatric Research, iPSYCH, Aarhus University, Fuglesangs Allé 4, Aarhus V, Denmark.
authors: Philip R
authors: PR
authors: Nielsen
authors: Michael E
authors: ME
authors: Benros
authors: National Centre for Register-Based Research, Aarhus University, Fuglesangs Allé 4, Aarhus V, Denmark; The Lundbeck Foundation Initiative for Integrative Psychiatric Research, iPSYCH, Aarhus University, Fuglesangs Allé 4, Aarhus V, Denmark.
authors: Carsten B
authors: CB
authors: Pedersen
authors: National Centre for Register-Based Research, Aarhus University, Fuglesangs Allé 4, Aarhus V, Denmark; The Lundbeck Foundation Initiative for Integrative Psychiatric Research, iPSYCH, Aarhus University, Fuglesangs Allé 4, Aarhus V, Denmark.
authors: Preben B
authors: PB
authors: Mortensen
mesh_terms: D000293:Adolescent; D000328:Adult; D001930:Brain Injuries / Q000453:epidemiology*; D002318:Cardiovascular Diseases / Q000453:epidemiology*; D015897:Comorbidity; D003718:Denmark / Q000453:epidemiology; D004827:Epilepsy / Q000453:epidemiology*; D005260:Female; D005500:Follow-Up Studies; D006761:Hospitals / Q000706:statistics & numerical data; D006801:Humans; D008297:Male; D008659:Metabolic Diseases / Q000453:epidemiology*; D012559:Schizophrenia / Q000453:epidemiology*; D055815:Young Adult
keywords: physical illness; risk factors; schizophrenia