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Dávid Erbszt

August 8th, 2024

The DNA of Trauma

0 comments | 3 shares

Estimated reading time: 5 minutes

Dávid Erbszt

August 8th, 2024

The DNA of Trauma

0 comments | 3 shares

Estimated reading time: 5 minutes

In this series we publish blog posts written by our undergraduate students for the PB101 Foundations of Psychological Science course. Here, Dávid Erbszt explores transgenerational trauma and considers the evidence for epigenetic transmission of trauma in humans. 

Sometimes a tragic historical event can have even deeper consequences than one might assume. When the psychological distress caused by a traumatic historical event spans multiple generations, we talk about transgenerational trauma. Recently, scientists have been trying to establish a link between genetics and psychological wounds, but is it really possible to pass on the ‘trauma gene’?

The effects of transgenerational trauma are well-documented within multiple social groups that have historically faced collective trauma. This piece will focus on the Holocaust due to the vast scientific literature that already exists on the topic, but it is important not to forget about the experiences of other social groups. The effects of slavery on African American people, the colonisation of indigenous peoples of the world, and the Holodomor for Ukrainians, for instance, can all be examined as cases of transgenerational trauma.

Inherited Holocaust trauma

In 1966, Canadian researchers reported for the first time that children of Holocaust survivors are more likely to suffer from mental hardships – a finding that has been corroborated many times since then (Rakoff et al., 1966, cited in DeAngelis, 2019). Recent research has found that offspring of Holocaust survivors have higher rates of anxiety, depression and Post-Traumatic Stress Disorder (PTSD); while having two survivor parents instead of only one increases the severity of mental health problems their children face (DeAngelis, 2019; Dashorst et al., 2019). Parent-child relationships can be greatly altered by the looming effects of Holocaust trauma as well; research has shown that parental Holocaust experiences can lead to insecure attachment styles in children and unfavourable psychological development (Dashorst et al., 2019). The reversal of parent-child roles and the insufficient ability to provide emotional and physical care have both been identified as characteristics of the parenting styles of Holocaust survivor parents (Dashorst et al., 2019).

It is clear that Holocaust trauma can be passed on between generations – it is present in parenting, attachments and communication, and leads to tangible consequences in the form of an increased likelihood of suffering from mental problems. But how does transmission happen? Social influences undoubtedly play a huge role as multiple researchers have pointed out; parents with histories of trauma use language that discourages their children from trusting people, almost as if they were in ‘survival mode’ at all times, for instance (DeAngelis, 2019). There is no debate that trauma can be transmitted via parental interactions, but there may be more factors if one looks under the surface. Many scientists would argue that epigenetic mechanisms should not go unnoticed.

What is epigenetics?

The field of epigenetics examines alterations in gene expression that do not involve changing the genetic code itself. It can best be understood by imagining switches attached to genes that can be turned on and off when prompted by external influences (Gray and Bjorklund, 2018). For instance, identical twins, and even cloned animals, look different from each other right at the time of birth. Since they are supposed to share the same genetic code, the differences between newborn babies and cloned animals can be explained by differences in gene expression, which is what epigenetics is concerned with.

Epigenetic inheritance in mammals

Dias and Ressler (2014) made waves in the scientific community when they apparently demonstrated epigenetic inheritance in mice. They trained a group of mice to fear the smell of cherry blossom by delivering small electric shocks whenever they came across the smell (Dias and Ressler, 2014). Interestingly, their offspring also had a fearful reaction to the smell of cherry blossom despite never having encountered it before, and even some of the offspring’s offspring reacted the same way (Dias and Ressler, 2014). Environmental stressors, such as the trauma associated with the smell of cherry blossom, thus influenced the gene expression of the offspring, leading to inherited fearful responses to the smell of cherry blossom across multiple generations. Although this study was conducted on mice, the findings offer a solid basis for optimism in demonstrating the same mechanism in humans. Hypothetically, the effects of traumatic historical events in humans could be transmitted the same way, which is what the following study attempted to demonstrate.

Epigenetics and the Holocaust

Yehuda et al. (2015) claimed to have demonstrated the epigenetic transmission of trauma in human subjects. The team of researchers examined 32 Holocaust survivors who suffered from PTSD, and their children, and reported that the offspring had a higher likelihood of stress disorders compared to children whose parents did not go through such a traumatic experience. Throughout their analysis, they ruled out the possibility of the children having experienced trauma themselves, and came to the conclusion that it could only be attributed to the epigenetic inheritance of Holocaust trauma, observed through changes in certain gene expression processes of the offspring (Yehuda et al., 2015). Additional research supports these findings; multiple studies have shown that parental trauma affects the offspring’s cortisol – the ‘stress hormone’ – mechanism through epigenetic processes (Kertes, et al., 2016; Dashorst et al., 2019).

Sceptical voices, optimistic future

Seeing how ground-breaking these ideas are, it is no surprise that they were met with scrutiny and greatly divided the scientific community (Callaway, 2013). The biggest obstacle is showing that the well-documented effects of parental trauma on the offspring’s mental health are the result of epigenetics, and not just social influences (Thomson, 2015). Critics of the study conducted by Yehuda et al. (2015) noted the small sample size of 32 and the even smaller control group, while also underlining the impossibility of fully controlling the breeding environment of humans (Birney, 2015). Although criticism must be recognised, the field of epigenetics is just getting started. Understanding the epigenetic mechanisms behind the transmission of trauma can tremendously deepen our knowledge of the genes associated with a higher likelihood of developing depression and anxiety. The discovery of epigenetic trauma transmission in mice and humans, although highly contested, is incredibly exciting for the field of psychology and opens the door for endless possibilities for future research.

  • This post was originally written as part of PB101: Foundations of Psychological Science, which is a core course on the BSc Psychological and Behavioural Science. It has been published with the permission of the author.
  • The opinions in this post are of the author, not of the Department of Psychological and Behavioural Science or LSE.
  • Cover image by GrumpyBeere from Pixabay.

References

  • Birney, E. (2015). Why I’m sceptical about the idea of genetically inherited trauma. The Guardian. Link.
  • Callaway, E. (2013). Fearful memories haunt mouse descendants. Nature. Link.
  • Dashorst, P. et al. (2019). “Intergenerational consequences of the Holocaust on Offspring Mental Health: A systematic review of associated factors and Mechanisms,” European Journal of Psychotraumatology, 10(1). Link.
  • DeAngelis, T. (2019). The Legacy of Trauma, Monitor on Psychology. American Psychological Association. Link.
  • Dias, B.G. and Ressler, K.J. (2013). “Parental olfactory experience influences behavior and neural structure in subsequent generations,” Nature Neuroscience, 17(1), pp. 89–96. Link.
  • Gray, P. and Bjorklund, D.F. (2018). Psychology. New York City, New York: Worth Publishers.
  • Kertes, D.A. et al. (2016). “Prenatal maternal stress predicts methylation of genes regulating the hypothalamic–pituitary–adrenocortical system in mothers and newborns in the Democratic Republic of Congo,” Child Development, 87(1), pp. 61–72. Link.
  • Khazan, O. (2018). Inherited trauma shapes your health. The Atlantic. Link.
  • Thomson, H. (2015). Study of holocaust survivors finds trauma passed on to children’s genes. The Guardian. Link.
  • Yehuda, R. et al. (2015). “Holocaust exposure induced intergenerational effects on FKBP5 methylation,” Biological Psychiatry, 80(5), pp. 372–380. Link.

About the author

Dávid Erbszt

Dávid Erbszt has just completed his studies in Sociology at LSE. He is looking forward to starting the MSc Psychology of Economic Life programme at the same university in September 2024.

Posted In: PB101 Foundations of Psychological Science

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