To examine prenatal and perinatal risk factors for subsequent development of schizophrenia and affective and reactive psychosis.
Three population based, case-control studies conducted within a Sweden-wide cohort of all children born during 1973-9. This was done by linking individual data from the Swedish birth register, which represents 99% of all births in Sweden, to the Swedish inpatient register.
Patients listed in inpatient register as having been first admitted to hospital aged 15-21 years with a main diagnosis of schizophrenia (n=167), affective psychosis (n=198), or reactive psychosis (n=292). For each case, five controls were selected.
Main outcome measures
Risks of schizophrenia and affective and reactive psychosis in relation to pregnancy and perinatal characteristics.
Schizophrenia was positively associated with multiparity (odds ratio 2.0), maternal bleeding during pregnancy (odds ratio 3.5), and birth in late winter (odds ratio 1.4). Affective psychosis was associated with uterine atony (odds ratio 2.2) and late winter birth (odds ratio 1.5). Reactive psychosis was related to multiparity (odds ratio 2.1). An increased risk for schizophrenia was found in boys who were small for their gestational age at birth (odds ratio 3.2), who were number four or more in birth order (odds ratio 3.6), and whose mothers had had bleeding during late pregnancy (odds ratio 4.0).
A few specific pregnancy and perinatal factors were associated with the subsequent development of psychotic disorder, particularly schizophrenia, in early adult life. The association of small size for gestational age and bleeding during pregnancy with increased risk of early onset schizophrenia among males could reflect placental insufficiency.
- The role of prenatal and perinatal risk factors in the development of schizophrenia and affective and reactive psychosis in early adult life were investigated by linking individual data from the Swedish birth and inpatient registries
- Adverse prenatal and perinatal factors were more common in patients with schizophrenia of early onset than in controls and seemed more important in the aetiology of schizophrenia than in that of affective and reactive psychosis
- Multiparity, bleeding during pregnancy, and small size for gestational age were associated with a threefold to fourfold increased risk for schizophrenia among males
- There was no support for previous claims that head circumference is small in preschizophrenic infants
- Late winter birth was associated with increased risk of both schizophrenia and affective psychosis