OBJECTIVE: The aim was to study whether early weaning from breastfeeding may be associated with increased risk of schizophrenia. METHOD: 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). CONCLUSION: 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.