Early environmental risk factors for schizophrenia

The existence of early environmental risk factors for schizophrenia is central to the notion of schizophrenia as a neurodevelopmental disorder and these risk factors represent some of the most challenging and interesting targets of schizophrenia epidemiology. This chapter discusses prenatal and perinatal risk factors for schizophrenia. The risk of developing schizophrenia has consistently been found to be increased (1.5 to 2-fold) among those born in cities compared with those born in rural Areas. Rhesus (Rh) incompatibility, characterized by an Rh-negative mother pregnant with an Rh-positive fetus, has been associated with an elevated risk for schizophrenia. Prenatal stress is associated with smaller head circumference, neonatal neurological impairment and behavior problems in childhood. The best evidence to date is for prenatal exposure to influenza and other respiratory infections, prenatal rubella, hypoxia-related obstetric complications and low birth weight or intrauterine growth retardation.