Can you inherit the emotional scars caused by trauma and stress experienced by your parents, or even your grandparents?
A growing body of evidence suggests that may be the case.
“Intergenerational damage” is the term often used to describe the harrowing psychological legacies such as from the Holocaust, apartheid in South Africa and the Stolen Generation in Indigenous Australians.
But now scientists are uncovering a new possibility, that we may also physically pass on trauma through our altered genes (where certain genes are “switched on” or “off”).
One of the latest studies to suggest this was based on analysis of the genes of more than 900 British boys and girls whose mothers had been abused physically by their fathers as children.
The study, published in the journal Epigenetics, used data from the Avon Longitudinal Study of Parents and Children, an ongoing project that started in the 1990s. The new analysis, by Syracuse University in New York, identified 903 mothers who said they’d been abused physically by their fathers.
Previous research had identified genetic changes in women who’d been abused. When the scientists examined DNA from the umbilical cord blood of the Avon study children, they found similar changes as those seen in abused women, suggesting altered genes had been passed on.
These alterations to genes are known as epigenetic changes — caused as a result of our environment or lifestyle such as, for example, smoking. Such changes can then alter our physical health or our emotional behaviour.
When the researchers examined the children’s school psychiatric reports at age seven, their levels of anxiety, fear and depression closely correlated with their inherited gene changes.
The idea that we could somehow inherit behaviours from previous generations was originally proposed more than 200 years ago, by the pioneering French biologist Jean-Baptiste Lamarck, but at the time his ideas were derided.
In recent years, though, lab experiments have begun to prove the worth of this theory in terms not just of the environment in which children are raised, but in actual changes to their DNA.
One game-changing study in 2010 found that when mouse pups were suddenly removed from their mothers, they grew up to show depressive-like behaviour and to be unusually fearful when put in new environments.
DNA tests showed the mice had epigenetic changes in genes associated with trauma and fear, according to lead researcher Isabelle Mansuy, a professor in neuro-epigenetics at the University of Zurich, Switzerland, writing in the journal Biological Psychiatry.
What’s more, when the male pups themselves sired offspring, these showed exaggerated fear and trauma reactions as well as gene changes, despite being raised in normal environments, Professor Mansuy reported.
More recently Rachel Yehuda, a professor of psychiatry and neuroscience of trauma at Mount Sinai School of Medicine in New York, found an epigenetic change in survivors of Nazi concentration camps and their offspring.
As her study pointed out, many Holocaust survivors have post-traumatic stress disorder (PTSD) and other emotional conditions. But she has now shown that it’s not ‘just’ the home environment that causes this, it is the inherited genes.
A 2016 study, published in the journal Psychological Trauma: Theory, Research, Practice, and Policy, found one in five children of Holocaust survivors had generalised anxiety, marked by uncontrollable, irrational worry.
But in a recent study with 32 survivors and 22 of their adult children, Professor Yehuda found epigenetic changes in the same region of the FKBP5 gene (linked to anxiety and other mental health concerns) in the survivors and their children.
The alterations were not found in a comparison group of Jewish parents and their children who had lived outside Nazi-occupied Europe.
As an evolutionary adaptation, increased vigilance and fear may help offspring survive threatening environments, says Professor Yehuda.
“If you’re living in adversity, you might have a skill-set to survive it that is honed from life lessons of the past. But if you’re not in adversity, you may become emotionally hypervigilant,” she says.
Fathers may pass on stress-given genetic alterations in their sperm, suggests a 2019 study by Queensland University of Technology.
When the researchers compared genes in the sperm of veterans with and without PTSD, they found epigenetic changes associated with stress and anxiety in the veterans’ now-adult children if their fathers had PTSD — but not in the others.
Professor Yehuda says this means a life-altering experience “doesn’t just die with you”.
“It has a life of its own afterwards in some form,” she says. “The implications are that what happens to our parents, or perhaps even to our grandparents, may help shape who we are on a fundamental, molecular level that contributes to our behaviours, beliefs, strengths and vulnerabilities.”
There may even be measurable physical effects in the brains of traumatised people’s children, according to research by Sakarya University in Turkey in 2022.
They scanned the brains of 40 children whose mothers were exposed as teenagers to an earthquake that struck Turkey in 1999.
When compared to scans from 27 children of mothers who hadn’t experienced the earthquakes, the trauma group had a significantly smaller amygdala and hippocampus in their brain.
These areas “play important roles in relation to post-traumatic physiological responses”, reported the journal Psychiatry Research: Neuroimaging. “Our study shows that there may be a potential relationship between intergenerational trauma and various brain structures.”
Chloe Wong, a senior lecturer in epigenetics at King’s College London, believes inherited stress can have a big impact on our lives.
“Children of traumatised mothers inherit that stress in the womb,” Dr Wong says. “Studies have even shown that their DNA changes are different, depending on their age in the womb when the stress happened.”
She adds that research has also shown inherited stress may even accelerate the speed at which your body and brain age.
Not everyone is convinced about the strength of this relationship, however. Heather Sequeira, a consultant psychologist with a special interest in trauma, based in London, says traumatised parents’ behaviour may have a much stronger influence on their children’s mental health than any genetic inheritance.
“It is impossible to disentangle parents’ emotional influence from epigenetic transmission,’ she says. ‘They are entangled. It’s multi-faceted and intertwined.”
Failure by traumatised mothers to bond with their babies early on might have a particularly strong influence.
Dr Sequeira says: “Being brought up by someone who does not feel safe and relaxed can have a serious effect in transmitting traumatic feelings. In the first three to five weeks of life, the baby’s nervous system is in its crucial stage. Not forming strong parental bonds can impact on subsequent psychological development.”
But whether those stresses can be passed on to grandchildren isn’t fully confirmed, adds Dr Wong. “Research suggests most of our epigenetic inheritance seems to get wiped away before the grandchildren’s generation.”
The good news, she says, is that studies show that “damaging epigenetic changes are reversible”.
Research by Professor Mansuy has found that when mouse pups who had been traumatised early in life were put into cages that had very richly supportive environments — with running wheels, toys, a maze and plenty of other mice to socialise with — their gene changes diminished and they didn’t show trauma symptoms. Their offspring didn’t, either.
Dr Wong explains: “We know that people who exercise, have a healthy diet and get plenty of good sleep have a younger epigenetic age. Everything you do might change your epigene for good or for bad.”
Dr Sequeira says the main threat is that epigenetic changes may lead to chronic inflammation, “one of the biggest dangers to brain and body”.
“Numerous studies show that such chronic inflammation can be quelled by healthy eating such as a Mediterranean-style diet, regular exercise, meditation, mindfulness — and not eating ultra-processed foods [because they are inflammatory]. It’s all the more reason to look after ourselves.”
And who knows, your grandchildren (and even their children) may ultimately thank you for it.