These perinatal risk factors include the following: Genetic disorders (particularly those that increase risk of childhood onset) Exposure to certain drugs or substances (eg, cannabis) during a vulnerable period Prenatal undernutrition Labor complications, hypoxia, perinatal infection, placental abruption or insufficiency Childhood brain injury Other risk factors, which occur later (eg, illicit drug use later in adolescence), may then trigger the onset of schizophrenia.