Experiencing trauma early in childhood can lead to mental health problems in adolescence and adulthood, but mild to moderate trauma could also have an unexpected upside for some survivors, making them better able to cope with stressful situations later in life.
Previous research has shown that the behavioral effects of trauma can be passed down to the next generation -- but this research had only demonstrated that this transmission takes place with trauma's negative effects, such as depression. Now a study on mice, recently published in the journal Nature Communications, suggests that the adaptive benefits of trauma might also stay alive in families through the years.
The University of Zurich researchers identified the molecular mechanisms by which the effects of trauma are transmitted from one generation to another. In some cases, the silver lining of a traumatic episode -- that is, learning to better cope with stress -- can also be passed down.
"This study builds on our previous work in mice showing that exposure to traumatic stress during early life has detrimental effects on behavior across generations -- it induces depression, antisocial behaviors, memory impairment, etc.," the study's lead researcher, neuroepigeneticist Isabelle Mansuy, said in an email to The Huffington Post. "We wondered if it may provide some benefit in certain conditions, such as in challenging situations."
To examine the effects and transmission of this benefit, the researchers put newborn male mice under traumatic stress by removing them from their mothers at regular intervals, which also put the mothers under significant stress. When the male mice were adults, they and their offspring underwent tests to analyze their behavior. The mice who had undergone early trauma were compared to a control group of mice who were not subjected to stress.
The researchers found that the trauma-exposed mice and their offspring were able to complete difficult tasks more efficiently than the mice in the control group. They were also found to have show improvements in goal-oriented behavior in difficult situations.
"Because they or their father were placed in challenging conditions when young, they developed strategies to more efficiently respond to future exposure later in life," Mansuy told The Huffington Post.
In both groups, the fathers were kept apart from the offspring and their mothers -- the offspring, then, could not have learned this behavior from their fathers and instead must have inherited it. The researchers then examined the activity of a gene implicated in flexible behavior, and found that "epigenetic marks" (which determine how much a gene is expressed) were altered in this gene, in the brain and the sperm of the stressed fathers. The altered marks were passed down to the mice's offspring.
"Our results show that environmental factors change behavior and that these changes can be passed on to the next generation," Mansuy said in a statement.
Although the researchers emphasize that they are not suggesting that childhood trauma is positive in any way, the findings do suggest that experiencing trauma -- if children are supported and able to cope effectively -- could have positive as well as negative cross-generational effects.