title: Breastfeeding and risk of schizophrenia in the Copenhagen Perinatal Cohort.
abstract: OBJECTIVE
  The aim was to study whether early weaning from breastfeeding may be associated with increased risk of schizophrenia.
  
  
  METHODS
  The current sample comprises 6841 individuals from the Copenhagen Perinatal Cohort of whom 1671 (24%) had been breastfed for 2 weeks or less (early weaning) and 5170 (76%) had been breastfed longer. Maternal schizophrenia, parental social status, single mother status and gender were included as covariates in a multiple regression analysis of the effect of early weaning on the risk of hospitalization with schizophrenia.
  
  
  RESULTS
  The sample comprised 93 cases of schizophrenia (1.4%). Maternal schizophrenia was the strongest risk factor and a significant association between single mother status and elevated offspring risk of schizophrenia was also observed. Early weaning was significantly related to later schizophrenia in both unadjusted and adjusted analyses (adjusted odds ratio 1.73 with 95% CI: 1.13-2.67).
  
  
  CONCLUSIONS
  No or <2 weeks of breastfeeding was associated with elevated risk of schizophrenia. The hypothesis of some protective effect of breastfeeding against the risk of later schizophrenia is supported by our data.
authors.affiliation: Department of Psychiatry, Amager Hospital, Copenhagen University Hospital, Denmark.
authors.forename: H J
authors.initials: HJ
authors.lastname: Sørensen
authors.forename: E L
authors.initials: EL
authors.lastname: Mortensen
authors.forename: J M
authors.initials: JM
authors.lastname: Reinisch
authors.forename: S A
authors.initials: SA
authors.lastname: Mednick
mesh_terms: D000328:Adult; D001942:Breast Feeding / Q000706:statistics & numerical data*; D002391:Catchment Area, Health; D015331:Cohort Studies; D003718:Denmark / Q000453:epidemiology; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D008297:Male; D009035:Mothers / Q000523:psychology / Q000706:statistics & numerical data; D012307:Risk Factors; D012559:Schizophrenia / Q000453:epidemiology*; D012737:Sex Factors; D015406:Single Parent / Q000523:psychology / Q000706:statistics & numerical data; D012923:Social Class; D014886:Weaning