Conventionally we’ve been taught that most of our traits are determined by our DNA. Beyond physical traits such as our height and the colour of our eyes, character traits such as whether we’re extroverts or introverts are also somewhat dictated by our DNA. But how about our life experiences? Could they potentially be inherited? In 1942, this idea was unpacked by C.H. Waddington, a scientist who coined the term ‘Epigenetics’, which literally meant ‘beyond the genome’. This field of study did not just focus on an individual’s DNA sequence (genotype), it specifically aimed to understand how the very environment we lived in and the experiences we had could switch certain genes on or off (phenotype). These changes in gene expression would then be passed onto future generations.
One of the Waddington’s earliest epigenetics experiments involved fruit flies that were subjected to environmental stress, such as extreme temperatures. The environmental stress triggered a change in the fruit flies. They had four wings instead of two and these changes were passed on to generations that followed, even without the presence of the original stimulus. Decades later, the field of epigenetics has expanded and taken the world of science by storm. Today, there is large amount of research dedicated to epigenetic mechanisms in relation to a wide variety of illnesses and behaviours including cancers, cognitive dysfunction and neurobehavioral problems. Apart from illnesses, there is also a growing interest in how trauma can result in epigenetic alterations in children. Fathers who have experienced a traumatic life event may have children who have an increased risk of anxiety, depression or obsessive-compulsive disorder, even though the children may have never experienced trauma in their lifetime. In this way, epigenetics sheds new light on how our present-day experiences may shape the lives and experiences of our descendants.
Indeed, there is evidence that the second and third generation descendants of Holocaust survivors can be plagued by terrible nightmares, debilitating anxiety, and depression. This intergenerational transmission of trauma is clearly described in “Children of the Holocaust: Conversations with Sons and Daughters of Survivors” – a book written in 1979 by a second-generation holocaust survivor. The survivor stated that she always felt a “floating sense of danger” due to the vivid images of the “piles of skeletons” which kept haunting her, even though she had witnessed none of those.
Similarly, intergenerational consequences of psychiatric disorders were observed in the children of Finnish women who were given to Swedish foster families during World War II. However, none of these mental health issues were seen in the offspring of mothers who stayed with their parents at the time. Likewise, a recent study conducted by Costa and colleagues found that the trauma experienced by prisoners during the US civil war (POW) was seemingly passed down to future generations. They observed that the sons of ex-POWs were more likely to die young compared to the sons of non-POWs, even though these children were born after the war.
Yet, how exactly are these characteristics inherited? It turns out that as a result of environmental stress or psychological trauma, the DNA or histone proteins (around which DNA wraps around) are flagged with a chemical marker called a methyl group. When this marker is attached to the DNA or protein, the genes in that region are turned off. When the gene is turned off, what results is a memorable imprint of the traumatic experiences on the epigenome, which can be passed on to subsequent generations. In 2009, McGill University and Douglas Institute scientists captured this biological mechanism by studying a sample of 36 brains. Of those brains, they inspected the brains of those who were abused in childhood and found that all of them had a common pattern of epigenetic markings on the DNA of their hippocampus, a part of the brain involved in the formation of memories. Based on these markings, certain receptors that trigger the stress response would be activated, increasing the risk for suicide.
Controversy surrounds the field of epigenetics and studies on inherited trauma for a multitude of reasons. One of these reasons is that many of these studies only been able to test the effect of epigenetics over two generations. However, four generations need to be studied (great-grandchildren of survivors) to prove that epigenetic changes are actually passed on across generations. In addition, the children born to holocaust survivors grow up listening to horrific war stories, which in and of itself can lead to anxiety and depression in adulthood. So, the questions become: how can the bias of these stories be teased out from the influence of epigenetics? Also, is DNA methylation the cause or the result of trauma? And, is DNA methylation the cause or the result of trauma?
With all of this being said, it is clear that as well researched as epigenetics is, the field’s applicability to the experience of trauma is still premature. Thus, we require a better understanding of the epigenetic transmission of trauma before we can diagnose, prevent, and effectively treat trauma genetically (if at all). Furthermore, the presence of trauma does not always mean that it is going to be transmitted to offspring. However, if the trauma is transmitted, it can be managed through environmental manipulation, such as low stress in adult life as well as natural human resilience. Clearly, epigenetics makes a strong case for just how long-lasting abuse can be and perhaps will be increasingly used in arguments against war and other global atrocities.
By Ishaan Sachdeva
Please note that opinions expressed are the author’s own. They do not necessarily reflect the views and values of The Blank Page.
