The study, which looked at adults whose parents had either evacuated or remained in Finland as children during World War II, found that daughters of female evacuees had the same high risk for mental health disorders as their mothers, even though they had not faced the same trauma.
The study was conducted by researchers at the National Institutes of Health, Uppsala University in Sweden, and Helsinki University in Finland.
Although the study did not determine why this risk persists across generations, possible explanations include changes in the evacuees’ parenting behavior resulting from their childhood trauma 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 study author Stephen Gilman, Sc.D., of the Division of Intramural Population Health Research at the Eunice Kennedy Shriver National Institute of Child Health and Human Development.
“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.”
From 1941 to 1945, approximately 49,000 Finnish children were evacuated from their homes into Swedish foster homes in order to protect them from bombings, malnutrition, and other hazards during war with the Soviet Union.
Many of these children were only preschool age. These children faced the trauma of separation from their families, adapting to their new foster families, and in many cases, learning a new language. Upon their return, many of these children experienced the additional stress of re-adjusting to Finnish society. On the other hand, thousands of Finnish families chose not to evacuate all their children and often kept some at home.
For the study, the researchers compared the risk of being hospitalized for a psychiatric (mental health) disorder among offspring of the evacuees to the risks of psychiatric hospitalization among the offspring of the siblings who remained with their parents.
Studying both groups 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.
Findings from a previous study had shown that children who had been evacuated were more than twice as likely to be hospitalized as an adult for a psychiatric disorder than their female siblings who remained at home.
For the current study, the researchers linked the records of 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 findings show that female evacuees and their daughters were at the greatest risk for being hospitalized for mood disorders, such as depression and bipolar disorder. In fact, the daughters of evacuees faced more than four times the risk of hospitalization for a mood disorder, compared to the daughters of mothers who stayed home — regardless of whether their mothers were hospitalized for a mood disorder.
The researchers did not find any increase in psychiatric hospitalizations for the sons or daughters of males who had been evacuated as children.
While the study could not determine why the daughters of female evacuees faced a greater risk, one possibility is that the evacuation trauma may have impacted their mental health in ways that influenced their parenting style.
Another possibility is that the evacuee experience resulted in epigenetic changes. For example, previous research has shown that Holocaust survivors have higher levels of compounds known as methyl groups bound to the gene FKBP5 and have passed this change on to their children. This higher level of methyl groups appears to alter the production of cortisol, a hormone that regulates the stress response.
“The Finnish evacuation was intended to protect children from the many harms associated with the country’s wars with the Soviet Union,” said study co-author Torsten Santavirta, Ph.D., of Uppsala University. “Our observation of long-term psychiatric risk that reached into the next generation is concerning and underscores the need to weigh benefits as well as potential risks when designing policies for child protection.”
The researchers conclude that more studies are needed to understand how the experience of war impacts the mental health of parents and their offspring and to develop interventions to help families affected by armed conflict.