Mental illness associated with early childhood adversity may be passed from one generation to another, according to a study of adults whose parents evacuated Finland as children during World War II. Researchers found that daughters of female evacuees had the same high risk for mental health disorders as their mothers, even though they did not experience the same adversity. The study by researchers at Uppsala University in Sweden and Helsinki University in Finland could not determine why the higher risk for mental illness persisted across generations. Possible explanations include changes in the evacuees’ parenting behaviour stemming from their childhood experience or epigenetic changes – chemical alterations in gene expression, without any changes to underlying DNA.
“Many studies have shown that traumatic exposures during pregnancy can have negative effects on offspring,” said Stephen Gilman, from Eunice Kennedy Shriver National Institute of Child Health and Human Development in the US. “Here, we found evidence that a mother’s childhood traumatic exposure – in this case separation from family members during war – may have long-lasting health consequences for her daughters,” said Gilman, author of the study published in the journal JAMA Psychiatry. From 1941 to 1945, roughly 49,000 Finish children were evacuated from their homes to protect them from bombings, malnutrition and other hazards during the country’s wars with the Soviet Union, researchers said.
The children, many of them only preschoolers, were placed with foster families in Sweden. In addition to separation from their families, the children faced the stresses of adapting to their foster families, and in many cases, learning a new language. Upon their return, many children experienced the additional stress of readjusting to Finnish society. The researchers compared the risk of being hospitalised for a psychiatric (mental health) disorder among offspring of the evacuees to the risks of psychiatric hospitalisation among the offspring of the siblings who remained with their parents. Studying the two groups – cousins to each other – allowed the researchers to compensate for family-based factors that can contribute to mental health problems and to focus instead on the evacuees’ wartime experience.
In a previous study, the researchers found that women evacuated as children were more than twice as likely to be hospitalised for a psychiatric disorder than their female siblings who remained at home. For the current study, the researchers linked records from this generation – more than 46,000 siblings born between 1933 and 1944 – to those of their offspring, more than 93,000 individuals born after 1950. Of these, nearly 3,000 were offspring of parents who had been evacuated to Sweden as children, and more than 90,000 were offspring of parents who remained in Finland during the war.
The researchers found that female evacuees and their daughters were at the greatest risk for being hospitalised for mood disorders, such as depression and bipolar disorder. The evacuees’ daughters had more than four times the risk of hospitalisation for a mood disorder, compared to the daughters of mothers who stayed home – regardless of whether their mothers were hospitalised for a mood disorder.