Are there any risk factors that may precipitate schizophrenia?

While the cause of schizophrenia is not understood, some risk factors have been identified. These include a family history of schizophrenia, stressful life circumstances during childhood, older parental age at birth, use of illicit drugs during adolescence and perhaps exposure of the mother to certain virus or toxins during pregnancy. Again, these are only speculations and no one really knows why or how the disorder occurs.