title: Toxoplasma gondii as a risk factor for early-onset schizophrenia: analysis of filter paper blood samples obtained at birth.
abstract: BACKGROUND
  Infections during fetal life or neonatal period, including infections with Toxoplasma gondii, may be associated with a risk for schizophrenia and other mental disorders. The objectives of this study were to study the association between serological markers for maternal and neonatal infection and the risk for schizophrenia, related psychoses, and affective disorders in a national cohort of newborns.
  
  
  METHODS
  This study was a cohort-based, case-control study combining data from national population registers and patient registers and a national neonatal screening biobank in Denmark. Patients included persons born in Denmark in 1981 or later followed up through 1999 with respect to inpatient or outpatient treatment for schizophrenia or related disorders (ICD-10 F2) or affective disorders (ICD-10 F3).
  
  
  RESULTS
  Toxoplasma gondii immunoglobulin G (IgG) levels corresponding to the upper quartile among control subjects were significantly associated with schizophrenia risk (odds ratio [OR] = 1.79, p = .045) after adjustment for urbanicity of place of birth, year of birth, gender, and psychiatric diagnoses among first-degree relatives. There was no significant association between any marker of infection and other schizophrenia-like disorders or affective disorders.
  
  
  CONCLUSIONS
  Our study supports an association between Toxoplasma gondii and early-onset schizophrenia. Further studies are needed to establish if the association is causal and if it generalizes to cases with onset after age 18.
authors.affiliation: National Centre for Register-Based Research, University of Aarhus, Aarhus, Denmark. pbm@ncrr.dk
authors.forename: Preben Bo
authors.initials: PB
authors.lastname: Mortensen
authors.forename: Bent
authors.initials: B
authors.lastname: Nørgaard-Pedersen
authors.forename: Berit Lindum
authors.initials: BL
authors.lastname: Waltoft
authors.forename: Tina L
authors.initials: TL
authors.lastname: Sørensen
authors.forename: David
authors.initials: D
authors.lastname: Hougaard
authors.forename: E Fuller
authors.initials: EF
authors.lastname: Torrey
authors.forename: Robert H
authors.initials: RH
authors.lastname: Yolken
mesh_terms: D000818:Animals; D000913:Antibodies, Protozoan / Q000097:blood*; D016022:Case-Control Studies; D015331:Cohort Studies; D018672:Community Health Planning; D016001:Confidence Intervals; D003718:Denmark / Q000453:epidemiology; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D008297:Male; D019964:Mood Disorders / Q000097:blood / Q000401:mortality; D015997:Neonatal Screening; D011247:Pregnancy; D015597:Pregnancy Complications, Parasitic; D012189:Retrospective Studies; D012307:Risk Factors; D012559:Schizophrenia / Q000097:blood* / Q000453:epidemiology / Q000382:microbiology*; D014122:Toxoplasma / Q000276:immunology*
chemical_list: D000913:Antibodies, Protozoan