Children of women who undergo an emotionally stressful event during the first trimester of pregnancy appear more likely to develop schizophrenia, finds a study in the Archives of General Psychiatry.
The causes of schizophrenia are not well understood, but many researchers suspect that a combination of genetic risk factors and environmental triggers come into play.
Recent research suggests that events that affect mothers early in pregnancy, when their babies' brains are just beginning to form, may lead to the brain abnormalities that mark schizophrenia.
Emotionally traumatic events during pregnancy have been linked to other problems in children, such as an elevated risk of low birth weight and prematurity.
Researchers from the University of Manchester set out to find out whether the traumatic event of the death of a close relative affected rates of schizophrenia in the children of pregnant mothers in Denmark.
They looked at 1.38 million Danish births between 1973 and 1995. Using a national registry, the researchers were able to see whether any close relatives of pregnant women died or received a diagnosis of cancer, heart attack or stroke.
Their children were then tracked to see if they developed schizophrenia.
The researchers found that the risk of a child developing schizophrenia or a related disorder was about 67 per cent greater if their mothers had been exposed to the death of a relative during the first trimester.
But the rates were no higher if the mother experienced the trauma at any other time during pregnancy.
As well, a mother who experienced a relative going through a serious illness did not appear to have any greater risk of having a child with schizophrenia. The researchers also found that the link between a family death and risk of schizophrenia was only significant in families without a family history of mental illness.
The authors say it's not clear why a highly stressful event in early pregnancy would affect the chance that her baby would develop schizophrenia, but it's possible that chemicals released by the mother's brain in response to stress may affect the baby's developing brain.
These effects may be strongest in early pregnancy, when protective barriers between the mother and fetus are not fully constructed.
