An Epigenetic Epicenter: The Genetics of Trauma

Introduction

Intergenerational trauma is defined by the American Psychological Association as “the transmission of trauma or its legacy, in the form of a psychological consequence of an injury or attack, poverty, and so forth, from the generation experiencing the trauma to subsequent generations.”  In other words, people directly affected by adversity can pass their trauma onto their offspring.  Interestingly, there is evidence to support the idea that this phenomenon is actually biological.  The field of epigenetics studies variations in gene expression that may be responsible for intergenerational trauma.  In this article, we will be discussing the relationship between epigenetics and the heritability of post-traumatic stress.

What is trauma?

Trauma is any upsetting experience that results in anxiety, fear, dissociation, and other strong emotions that have the potential to negatively affect a person long-term.  It can be the result of human behavior, natural disasters, accidents, and other disturbing events.

There are three types of stress that a person can experience: positive, tolerable, and toxic.

• Positive stress is brief and characterized by a short-lived increase in heart rate and hormone levels.  It is completely normal and can actually facilitate growth.  Some examples include a child’s first day at school or a fearful response to receiving a vaccine.  

• Tolerable stress is longer-lasting and initiates the body’s stress reaction system to a greater degree than in positive stress.  This could be a scary injury or the loss of a loved one.

• Toxic stress, which occurs when stress signals are excessive and long-term, can alter the anatomy of the brain and disrupt other bodily functions when experienced in childhood.  Abuse, financial hardship, natural disasters, and other frequent and/or prolonged hardship may be considered toxic stress.

Toxic stress and trauma often go hand-in-hand, potentially affecting the development of organs in children and leading to an increased risk of heart disease, immune disorders, mental health conditions, and pain syndromes in adulthood.

What are epigenetics?

The field of epigenetics investigates changes in gene expression that have no impact on the genetic code itself.   It can be imagined as a light switch that is turned on and off by external influences, via a process called methylation.  Cloned animals and identical twins look slightly different even though they share the exact same genetic code because gene expression is varied, which is a perfect example of epigenetics at work.

As part of a 2014 study, researchers trained mice to fear the smell of cherry blossoms by shocking them whenever they were presented with the scent.  Their offspring also demonstrated a phobia of cherry blossoms, even though a shock was never delivered.  These findings can hypothetically be extrapolated to humans and the possible heritability of trauma.

Evidence in humans

In 2015, a team of researchers studied 32 Holocaust survivors with PTSD, as well as their children.   The findings suggest that the children had an increased likelihood of struggling with stress disorders.  Additional studies have found that trauma in parents can influence the children' s cortisol level.  Cortisol is an essential hormone for many bodily functions, but is also colloquially referred to as “the stress hormone” because it is released when a person experiences acute, chronic, or traumatic stress.  

On the  contrary

The main point of contention in regards to the epigenetic theory of trauma is that it is difficult to prove that these well-established links are the result of gene expression and not environmental influence.  The studies referred to above were conducted on small sample sizes, and there is the argument that it is impossible to fully control the environment into which a child is born.  However, given that the field of epigenetics is relatively new, there is still so much research to be conducted, and therefore it is not realistic to rule out current findings.

Resources

American Psychological Association. (n.d.-a). APA Dictionary of Psychology. American Psychological Association. https://dictionary.apa.org/intergenerational-trauma

American Psychological Association. (n.d.-b). Trauma. American Psychological Association. https://www.apa.org/topics/trauma

Holmqvist, T. (2024, October 7). The DNA of trauma - LSE psychological & behavioural science. London School of Economics and Political Science. https://blogs.lse.ac.uk/psychologylse/2024/08/08/the-dna-of-trauma/

Nie, Y., Wen, L., Song, J., Wang, N., Huang, L., Gao, L., & Qu, M. (2025, July 26). Emerging trends in epigenetic and childhood trauma: Bibliometrics and visual analysis. Frontiers in Psychiatry. https://www.frontiersin.org/journals/psychiatry/articles/10.3389/fpsyt.2022.925273/full

professional, C. C. medical. (2025, February 17). What does cortisol do?. Cleveland Clinic. https://my.clevelandclinic.org/health/articles/22187-cortisol

Toxic stress : What is toxic stress?. Center on the Developing Child at Harvard University. (2025, March 13). https://developingchild.harvard.edu/key-concept/toxic-stress/

Trauma & chronic stress relief. CMBM. (2024, June 26). https://cmbm.org/what-we-do/trauma-chronic-stress-mind-body-medicine/?gad_source=1&gad_campaignid=20790475835&gbraid=0AAAAADk1uh1o0ke3OCY_2YNkzX76XQQYO&gclid=Cj0KCQjwmqPDBhCAARIsADorxIZlUJkma74545g2Qho-q6L0o6SgkGXnKEMulI8Pe5LB3a2XZFTbzIMaApS7EALw_wcB

U.S. National Library of Medicine. (n.d.). Ep

igenetic modifications in stress response genes associated with childhood trauma. PubMed Central. https://pmc.ncbi.nlm.nih.gov/articles/PMC6857662/

Yehuda, R., & Lehrner, A. (2018, October). Intergenerational transmission of trauma effects: Putative role of epigenetic mechanisms. World psychiatry : official journal of the World Psychiatric Association (WPA). https://pmc.ncbi.nlm.nih.gov/articles/PMC6127768

Assessed and Endorsed by the MedReport Medical Review Board