Epigenetics & Generational Trauma

How can events in someone’s lifetime change the way their DNA is expressed, and how can that change be passed on to the following generations?

The question “How did your parents impact your life?” may trigger a diverse set of emotions within people, potentially ranging from gratitude to rage. However, most people will think of the answer in terms of (either or both of) the following two categories: nature and nurture. One, what did you inherit from your parents through genes (nature) and two, (if you were raised by your biological parents) how did they influence your life through their behaviour around/towards you (nurture)?

Did you know that there is a third category? Researchers classify the generational effects through epigenetics as “psychobiological”.

Let’s get into it:

What is Epigenetics?

Epigenetics is the study of changes in organisms caused by modification of gene expression rather than alteration of the genetic code itself. In other words, epigenetics is the change in how a gene is expressed, it is not a change in the gene itself. For example, not all of the genes we have are active at all times. Some are dormant until environmental impact (e.g., pharmaceutical chemicals, stress, drugs, trauma, or radiation) “flip the switch” and turn them on. This is called methylation and is one of the epigenetic mechanisms.

“Epigenetics is the alteration in the way that genes function.” – Prof Rachel Yehuda

Through epigenetics, the readability or expression of genes can be modified, offering a way of adapting to changing conditions without causing a more permanent shift in the DNA code itself. Tiny chemical tags are added to or removed from our genetic code in response to changes in our environment.

Mehmet Oz once said, “Your genetics load the gun, your lifestyle pulls the trigger.” For today’s topic, I suggest replacing “lifestyle” with “environment,” but you get the idea—our environment and experiences are substantial factors in the state and trajectory of our lives.

We will look into real-life examples below, but first, let’s define:

What is generational trauma?

To an extent, it’s self-descriptive: Generational trauma is the transmission of trauma to subsequent generations. If a person has experienced traumatic events (e.g., abuse or poverty), the harm caused can be experienced in successive generations, even if the children did not experience these traumatic events themselves.

Our ancestors’ trauma can significantly impact our own psychological and physiological functioning. The list of consequences is long, but to give you a few examples: increased anxiety, heightened sense of vulnerability and helplessness, low self-esteem, depression, hypervigilance, intrusive thoughts, difficulty with relationships and attachment to others, difficulty in regulating aggression, and extreme reactivity to stress.

The specific trauma reactions can vary, but overall, the effects mostly impact relationship skills, personal behaviour, and self-regulation difficulties.

How do our life experiences influence our children’s gene expression?

The science of the epigenetic inheritance of the effects of trauma is young and difficult to study. As you can imagine, researchers are not allowed to inflict trauma onto participants, which would allow for trauma to be isolated as a variable and to control for other factors. However, scientists ran animal studies and researched individuals and groups who have experienced trauma through different life circumstances.

Here is what we have learned:

The Cherry Blossom Experiment

Researchers delivered mild electric shocks to male mice while exposing them to cherry blossom scent. Over several repetitions, the mice associated this smell with pain (classical conditioning). It was shown that this fear response was accompanied by epigenetic changes in the mouse’s brain and sperm.

Shortly afterward, the males bred with female mice, and the offspring showed signs of distress in response to the cherry blossom smell despite never having experienced electric shocks themselves. To rule out that the pups were somehow learning about the smell from their parents, they were raised by unrelated mice who had never smelled cherry blossom.

These effects persisted for two generations. However, researchers flagged that the next generations do not always show exactly the same trait as their (grand)parents. For example, in subsequent generations, mice showed a heightened sensitivity to cherry blossom but not necessarily fear. Researchers found that the pups of the following generations had a greater number of neurons that detect the cherry blossom scent compared with control mice. They also found chemical markers on a gene related to smell receptors.

Evolutionarily, this makes sense as the offspring is now better equipped to sense danger more effectively. Darwin must be pleased with this finding, as his statement “survival of the fittest” suggests that organisms best adjusted to their environment are the most successful in surviving. Researchers argue that epigenetic responses may serve as an adaptation that might help the children of traumatized parents cope with similar adversities.

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Epigenetic Transmission of Holocaust Trauma

Professor of psychiatry and neuroscience, Rachel Yehuda, established a Holocaust research centre to study the effects of Holocaust trauma on subsequent generations. She states: “Survivors’ adult children were more likely than others to have mood and anxiety disorders, as well as PTSD. Further, many Holocaust offspring also had low cortisol levels—something that we had observed in their parents with PTSD.”

Overall, the research suggests that the offspring may have been marked epigenetically with a chemical coating on their chromosomes, representing a kind of biological memory of what the parents experienced. As a result, some suffer from a general vulnerability to stress.

The Dutch Famine

To recap, the Dutch famine (also known as the Dutch Hunger Winter) occurred for six months at the end of World War II in the Netherlands when the Nazis cut off food supplies to the western part of the country.

Research has found that children who were in-utero during this period had higher rates of health issues, such as cardiovascular diseases, diabetes, and obesity. These health problems were linked to epigenetic changes, specifically alterations in DNA methylation, which occurred due to the malnutrition experienced by their mothers during pregnancy. Overall, the epigenetic modifications affected genes involved in growth and metabolism, leading to higher rates of diseases in the offspring and, in some cases, even in the grandchildren of those who lived through the famine.

A note on generational trauma research:

The American Psychological Association states: “Research on generational trauma concentrated initially on the children, grandchildren, and great-grandchildren of survivors of the Holocaust and Japanese American internment camps, but it has now broadened to include the impact of slavery and structural racism on Black people, as well as the historical trauma experienced by American Indian communities, the families of Vietnam War veterans, and others.”

In Summary

Trauma can lead to epigenetic changes that alter gene expression. These changes can affect not only the individual but also their offspring, influencing stress responses and vulnerability to mental health disorders. Wars, famines, and genocides are all thought to have left an epigenetic mark on the descendants of those who lived through them.

My Thoughts

Personally, I am glad that the topic of trauma is increasingly recognized and discussed in mainstream media. However, I still think there is a long way to go until we (i.e., wider society) truly understand the impact trauma has on a person’s life. The consequences of trauma can heavily impact a person’s reality and quality of life, and I think we have yet to develop an appropriate understanding and compassion for individualistic circumstances. After all, trauma impacts the functioning of the brain and body.

Today, epigenetics is relatively new and controversial, just like PTSD (post-traumatic stress disorder) once was. Prof Rachel Yehuda states that “for some reason, we seem to have a hard time understanding and acknowledging the long-term and generational impact of trauma.” This does not mean that trauma cannot be healed, but that’s a conversation for another day!

Did you know about epigenetics before? If you have any questions or thoughts you would like to share, find me on instagram @neuroscience.musings.

Have a great day!! 

Best regards,

Sarah

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