There is an increasing amount of evidence of a link between schizophrenia and early brain development with environmental factors, including those occuring during pregnancy, and susceptibility genes interacting to influence risk. A study of 1.38 million Danish births between 1973 and 1995 looked at women whose relatives had died or received a diagnosis of cancer, heart attack or stroke during the women's pregnancy then looked to see whether their children developed schizophrenia. The researchers found that the risk of schizophrenia and related disorders was approximately 67% greater among the children of women who were exposed to the death of a relative during the first trimester of their pregnancies. However, death of a relative up to six months before or at any other time during pregnancy was not related to an increased risk of schizophrenia and nor was exposure to serious illness in a relative. The association between a family death and risk of schizophrenia appeared to be significant only for individuals without a family history of mental illness. Chemicals released by the mother's brain in response to stress could have an effect on the fetus' developing brain and these effects may be strongest in early pregnancy when protective barriers between the mother and fetus are not fully constructed.
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