Research Suggests Trauma and Healing are Genetically Passed Through Generations
Epigenetics research is bringing a whole new meaning to the phrase "breaking the cycle."
Hiya!
Now is a pretty incredible time to be alive. There is so much happening! Sure, a lot of it is scary with climate change and politics and whatnot, but we’re also making unimaginable technological and scientific breakthroughs. We’re discovering answers to some of humanity’s longest-held questions and uncovering new layers of eternal debates — like which has more influence over us, nature or nurture? How much free will do we actually have?
Scientists believe the answers to these questions lie within us, specifically in our epigenetics. When the human genome was first sequenced in 2003, it unleashed a whirlwind of research that suggests we inherit far more than our stubbornness, eye color, or laugh from our parents. Growing evidence indicates other qualities of our parents and even grandparents, including mental health, longevity, and traumatic experiences, may also be genetically “hardwired” in us.
Epigenetics
Simply put, epigenetics is the study of gene expression, or how our genes are turned on and off, but there’s a far less scientific reason epigenetics is so exciting. As Moshe Szyf, a professor of pharmacology at McGill University, explains to Andrea Cooper of National Geographic,
“(Epigenetics) touches on all the questions that humanity has asked since it was walking on this planet.” Such as, "How much of our destiny is predetermined? How much of it do we control?"
Gene expression helps answer these questions because the molecular process increases the activity levels of some genes while dampening others by adding and removing chemical tags called methyl groups to gene proteins.
In other words, genetics, like eye color, determines which proteins are made, while epigenetics decides which proteins are activated. Isabelle Mansuy, a professor in neuroepigenetics at the University of Zürich, told Cooper that it’s a bit like the difference between hardware and software. The genome is the “hardware” required to function, but epigenetics is the “software” that instructs how the genes in the genome behave.
The Center for Disease Control (CDC) summarizes epigenetics as:
“Epigenetics is the study of how your behaviors and environment can cause changes that affect the way your genes work. Unlike genetic changes, epigenetic changes are reversible and do not change your DNA sequence, but they can change how your body reads a DNA sequence.”
While genetics are generally considered permanent, epigenetics constantly change based on various factors. Mansuy explains to Cooper that,
“All the time, in every cell, every moment, the epigenome is changing.”
Our epigenome reacts to a range of factors, not just the genetics we inherit but also environmental ones like nutritional deficiencies and chemical exposures. So, in a way, epigenetics is where the effects of Nature and Nurture come together by activating genetic proteins (nature) while also determining gene expression (nurture).
Since its discovery, experts have wondered whether experiences such as trauma, in addition to traits, could be genetically imprinted in the genes of offspring. And plenty of research over the last couple of decades suggests the answer is yes.
Evidence in Animals
To better understand how ancestral trauma might be transmitted from parents to their offspring, Brian Dias, associate professor in the University of Southern California’s developmental neuroscience and neurogenetics program, conducted a study in 2013 on mice.
Mice and rats are the ideal subjects for research looking into intergenerational trauma since their lifespans are significantly shorter than ours, and they can produce multiple litters a year.
Dias conducted a series of experiments which involved exposing mice to the scent of cherry blossoms and then linking the scent with a mild electric shock to induce a fear response to the odor. As a result, the mice predictably viewed the smell as a threat. Remarkably, the next two generations of mice that didn’t experience shocks with the cherry blossom scent still exhibited the same fear response as the parents that did experience the shocks.
Dias repeated the experiment in 2018 using an odor that smelled like almonds. The team also included a subgroup of mice for this study that experienced the shock with the scent but were later exposed to the smell without the shock. In time, this subgroup’s fear of the odor lessened until the mice no longer feared the scent of almonds. Incredibly, the offspring of this subgroup didn’t present a fear response to the smell either.
That said, other research suggests that “inheritance” doesn’t mean an offspring will always express similar signs of trauma as the parent’s. For instance, Mansuy and her colleagues at the University of Zurich analyzed the epigenetic effects of seperating mice mothers from their pups.
In 2018, Mansuy and her team discovered that the pups and the pup’s offspring had many behavioral changes, including memory deficits, increased risk-taking behaviors, and depression. Depression symptoms and memory decline continued for three generations, while an increase in risk-taking behaviors only started to diminish after the fifth generation.
So, what’s happening in the genome to cause this? When studying the genomes of the mice whose symptoms lessened, Munsuy discovered the DNA methylation had changed in the male offspring’s sperm and brain.
It’s not just mice, though.
Evidence In People
Even though humans live significantly longer than mice, scientists have discovered that intergenerational trauma occurs in humans, too. A study from 2018 discovered that male children of Civil War soldiers who spent time as war prisoners were more likely to die early after the age of 45 than the children of Civil War soldiers who weren’t prisoners of war.
Earlier, in 2015, Rachel Yehuda, an Endowed Professor of Psychiatry and Neuroscience of Trauma at the Icahn School of Medicine at Mount Sinai Medical School, New York, studied a gene called FKBP5, which is linked to mental health concerns like anxiety and the stress hormone cortisol, in the genome of Holocaust survivors and their adult children. They found that,
“Holocaust exposure had an effect on FKBP5 methylation that was observed in exposed parents as well in their offspring.”
DNA methylation is one way our epigenome activates our genes by adding a chemical mark to DNA; meanwhile, demethylation removes the mark, deactivating the gene.
Yehuda replicated and expanded the study in 2020, this time including a larger group of participants and evaluating additional variables, including the age and sex of the parent during the Holocaust. She examined DNA methylation and found the children whose mothers survived the Holocaust had lower DNA methylation levels in their FKBP5 gene compared to the Jewish control group whose parents didn’t experience the Holocaust.
In 2021, Yehuda and her team searched for changes in expressions within genes linked to the immune system and found epigenetic changes that weaken the barrier of white blood cells. This causes the immune system to interact with the central nervous system in ways it’s not supposed to. Such changes are linked to anxiety, autism, depression, and psychosis.
Another study, this one from 2019, searched for methylation differences in the sperm of male Vietnam war veterans from Australia who were experiencing Post Traumatic Stress Disorder (PTSD) and then compared it to the DNA of veterans without PTSD. The researchers discovered ten regions of DNA that had different methylation patterns between the veterans experiencing PTSD and those that weren’t.
These changed methylation patterns in the veterans with PTSD were linked to their children’s diagnosed mental health conditions. The team found specific patterns of DNA changes that can be inherited, especially ones related to our stress response.
Even in the few years since then, more research by Yehuda and others shows that male soldiers who experience PTSD from combat have specific epigenetic tags.
Yet, if you can believe it, traumatic experiences aren’t the only thing we can inherit. Our environment can also cause epigenetic changes.
Environment
Back in 2005, researchers studied whether exposing pregnant female rats to an agricultural fungicide called vinclozolin could influence the sex of the offspring. It didn’t, but the researchers did discover that the male offspring’s sperm started dying off when they were about a year old. Incredibly, the same thing happened for the next three generations.
In 2019, the same researchers conducted a similar study by exposing rats to glyphosate, an herbicide. This time, the chemical didn’t appear to affect the rats’ direct offspring, but the grandchildren and great-grandchildren had high rates of birth abnormalities and obesity, along with kidney, prostate, and ovarian diseases. The DNA methylation found in the males' sperm in these generations had alterations linked to a higher risk of these diseases.
Thankfully, it’s not all bad news. It turns out there’s a plot twist: Generational healing is a thing, too.
Generational Healing
I mentioned Dias’ study earlier, which found that after conditioning mice with a fear response by accompanying a pleasant odor with a slight shock, they could also remove the response by exposing the mice to the scent without the shock. Once healed, the mice no longer seemed to pass on a fear response to their offspring.
Similarly, Mansuy and her colleagues wondered whether an enriched environment could reduce trauma-related behavior. In 2016, the team conducted an opposite set of experiments. This time, the team took mice that had been traumatized early in life and put them with other mice in cages with toys, a maze, and running wheels. In time, the mice stopped showing trauma symptoms, and their offspring didn’t either.
Yehuda wrote an article published by Scientific American about her research in which she says:
“It is tempting to interpret epigenetic inheritance as a story of how trauma results in permanent damage. Epigenetic influences might nonetheless represent the body's attempts to prepare offspring for challenges similar to those encountered by their parents.
“As circumstances change, however, the benefits conferred by such alterations may wane or even result in the emergence of novel vulnerabilities. Thus, the survival advantage of this form of intergenerational transmission depends in large part on the environment encountered by the offspring themselves.”
In other words, as remarkable as the idea is that our traumatic experiences can be genetically inherited in a way, there seems to be an apparent biological reason for it to happen — Survival of the species.
Perspective Shift
Epigenetics is revolutionary for more reasons than I have time or space to discuss, but Hannah Critchlow of The Guardian points out perhaps the most influential one — its potential to significantly accelerate evolution.
As far as we know, we’re the only animals capable of working on goals or projects over multiple generations for the long-term benefit of future generations — a concept called “cathedral thinking.” Considering this, Critchlow writes that,
Our knowledge of epigenetics and its potential to massively speed up evolutionary adaptation could support us to do everything we can to be the ancestors our descendants need. Conflict, neglect and trauma induce unpredictable and far-reaching changes. But so do trust, curiosity and compassion. Doing the right thing today could indeed cascade across generations.
Unlike genetic factors that can’t be changed, epigenetically inherited behavior is within our power to reverse and overcome. We have the choice to heal and literally break the cycle of intergenerational trauma. Just imagine the ripple effects this healing could have on future generations.
You’re currently reading my free newsletter, Curious Adventure. If you want more, you’ll likely enjoy my other newsletter, Curious Life, which you’ve already received sneak peeks of on Monday mornings.
The subscription helps me pay my bills so I can continue doing what I love — following my curiosities and sharing what I learn with you. Also, if you enjoy my work and want to show me support, you can donate to my PalPal. Thank you for reading. I appreciate you.
I wonder when we will be able to study the “concreteness” of healing trauma by looking at our genes. It’s utterly fascinating and scary and so cool.
Fascinating! More evidence that the tapestry of life is connected.