Intergenerational Trauma Is a Biological Reality

Intergenerational Trauma Is a Biological Reality

Can we inherit the trauma of our ancestors and pass down our own trauma to later generations? Many have claimed this is the case, but for the first time, there seems to be an actual biological link bridging the gap between intergenerational trauma and the hard sciences.

Epigenetics, a groundbreaking and fast evolving field, says we can and in fact do. It offers answers to just how deeply social turmoil can impact populations and their descendants. From high suicide rates among Australian Aborigines and the legacy of slavery, to inherited post-traumatic stress disorder (PTSD) risk among Holocaust survivors, the implications of new research promise far-reaching consequences for communities around the world grappling with social and political upheaval.

The field triggers a host of critical questions, however. What can epigenetics tell us about how our descendants will deal with environmental changes based on our own response to climate change? Will Syrian refugees pass down their trauma to their children and grandchildren, and what will that mean for a future that has not yet been born?

Epigenetics: A Growing Field With Profound Health Implications

Epigenetics, a term coined in the 1940s, has resurfaced after decades in the context of describing social phenomenon, tragedies and mental health. Psychologists, activists, political scientists and pundits alike increasingly rely on this field to justify their beliefs and findings.

Due to the gap in knowledge between public perceptions of intergenerational trauma and the actual science, it is helpful to explain what epigenetics is and what the actual data show.

Though early studies related to epigenetics were limited to basic cell differentiation or how it develops and matures in yeast and bacteria, the field has since expanded to explain entire communities. Remarkably, this cutting-edge research suggests that the traumas experienced by our ancestors are perhaps inherited, influencing not only our own behavior but also the behavior of our unborn children and grandchildren.

One important study looked at the possible causes of high child suicide rates among Indigenous Australian populations. There were 77 suicides among Aboriginal and Torres Strait Islander populations just this year alone, with more than half occurring in victims under the age of 26 and some as young as 12. The study blamed intergenerational trauma for having “shaped” at least 13 of the deaths, representing nearly a quarter of all deaths.

A professor of Indigenous studies from the University of Western Australia, Pat Dudgeon, implicated the brutality of colonization on these Native populations. For example, the forced removal and separation of families, including young children from their parents, shapes how love is expressed and affection is displayed in communities, and influences later generations.

With the field now casting a wider net and getting increasing attention, it is important to understand what epigenetics really means to prevent misinformation or potential abuse. Anti-vaxxers, creationists and white supremacists have already added epigenetics to their vernacular and jargon to defend their controversial beliefs.

While numerous definitions abound, epigenetics is essentially what happens above the gene level. According to the National Institutes of Health, it is defined as “heritable changes in gene expression that are, unlike mutations, not attributable to alterations in the sequence of DNA.”

In other words, these are changes that affect our DNA but do not change its actual structure or composition. New epigenetics mechanisms continue to be discovered, but so far, we know that epigenetics has the ability to turn genes and their respective functions on and off in a process more analogous to a dial rather than a switch.

Epigenetics and its regulation of gene expression has been well-established in model organisms and humans. These changes are widespread and fine-tuned during normal development and are, at times, tissue-specific. However, dysregulation of these processes may lead to pathogenesis and disease, including cancer, Parkinson’s or heart disease.

More recently, studies have linked environmentally induced trauma to epigenomic changes, thereby affecting future generations. The vast majority of media coverage often cite the research of biochemist Rachel Yehuda. Yehuda found that male Holocaust survivors who suffered PTSD had children with lower levels of cortisol, an important hormone that helps regulate stress levels. Lower cortisol levels can increase the risk of PTSD.

In other words, the Holocaust victims’ memories, experiences and traumas influenced gene expression in their descendants. This could be applied to other traumas, including the transatlantic slave trade, inquisition or war on terror.

One key challenge to these findings is that they remain open to alternative interpretations. For example, Yehuda’s team found that if both of a child’s parents were Holocaust survivors with PTSD, the child was more likely to have lower levels of cortisol. But other researchers point to reverse causation as an alternative explanation: If there are significant levels of DNA methylation (the process which results in lower cortisol levels), is it caused by ancestral trauma, or does the presence of methylation itself increase the risk of PTSD?

Critics have called the conclusions of this study an “over-interpreted epigenetics study of the week.”

Other studies face similar critique, such as one highlighting glucose intolerance in the descendants of the survivors of the Dutch famine of 1944-1945.

Nonetheless, the growing body of research is important because it is a genuine attempt at answering the question of intergenerational trauma. Other studies in epigenetics have been extremely promising and show that certain traits linked to epigenetic changes, in worms and mice in particular, are being passed down.

These preliminary findings offer special insight into animal behavior that could one day be used to prevent or treat inherited trauma in humans. Siobhan O’Neill, a professor of mental health sciences at Ulster University, argues that the effect of intergenerational trauma could not only be reversed, but harnessed to make individuals stronger and healthier.

Glowing Worms

Last year, two teams of scientists in Spain were able to show that one trait in worms that causes them to glow under certain conditions was passed down to as many as 14 generations based on an environmental change affecting the worms.

Researchers used the C. elegans worm because it only takes about 50 days for 14 generations to develop, allowing scientists to observe how environmental genetic changes in animals are passed down in a relatively short period of time.

Worms that were exposed to warm water showed a higher activity of a certain transgene, a gene that is artificially introduced into an animal’s genome via genetic engineering. The transgene in this case involved a fluorescent protein. Placing the worms in a warmer climate significantly increased the activity of this transgene, causing the worms to glow brightly under ultraviolet light when viewed under a microscope.

Interestingly, when the worms were returned to the colder climate, they continued to express high activity of this transgene. Even more remarkably, the worms’ descendants also shared high activities of these transgenes, despite never being exposed to the warmer climate.
“Worms are very short-lived, so perhaps they are transmitting memories of past conditions to help their descendants predict what their environment might be like in the future,” study co-author Tanya Vavouri said in a statement.

Another study involved shocking mice after placing cherries near them, teaching them to associate the fruit’s smell with fear. The study found that their children and grandchildren became anxious and fearful when exposed to similar odors, suggesting an epigenetic link.

These developments help us to learn more about our own epigenetic inheritance. They may one day help to explain the impact of political and social upheaval on vulnerable populations.

Of course, mice and humans are different — but less different than we think. The Holocaust study mentioned above, for example, discovered that the NR3C1 gene was epigenetically modified and also exists in mice.

One significant challenge for researchers is following epigenetic changes in humans over a span of several generations, but several labs and studies are currently attempting to do just this.

Organizations in Philadelphia have already begun addressing trauma by educating policymakers and partnering with vulnerable communities. One such project is Philadelphia ACE, inspired and informed by studies finding a strong correlation between negative childhood experiences and intergenerational health. The organization has trained and educated policymakers, educators and professionals across the city. Earlier this year, for instance, after multiple tragedies involving city workers, a committee affiliated with the project was tasked with looking at how first responders themselves are adversely impacted by caring for traumatized people.

Such efforts mark a necessary step in the right direction, especially as more studies continue to provide the biological link to intergenerational trauma. But the question remains: Can we intervene in these epigenetic changes to make humans stronger? Possibly.