Can we inherit trauma?

Epigenetics allows for environmental factors to influence expression of our genes. Could this include emotional distress?

Writer: Zehra Beril Evcil
Editor: Dan Jacobson
Artist: Lucie Gourmet

Emotional trauma and stress can change a person; not only can these factors contribute to serious psychological and emotional damage, but they can alter the characteristics and genome expression of the progeny. 

Epigenetic studies show that the environment changes the expression of one’s genome via mechanisms such as DNA methylation. Methylation is a process where regions of DNA are switched off by the addition of methyl groups, inhibiting the binding of transcription factors (proteins that enable a gene expression) to the DNA. As gene expression changes, the cell itself changes. Although these changes are thought to be erased when fertilization occurs due to its washing-out effects.

While some researchers still believe that inherited epigenetics are caused by methylation, some suggest that small noncoding RNAs (sncRNAs) could have a role too. These noncoding molecules complement messenger RNAs, disrupting or amplifying their activity, but do not produce proteins like other RNAs. In other words, sncRNAs affect protein production.

Isabelle Mansuy, a researcher from the University of Zurich, believes that stress influences sncRNAs. She and her team conducted experiments on sncRNA from sperm cells, which are prone to stress. The main theory behind their research was that, when the sncRNAs have an effect on mother’s RNA, this could change the course of the zygote’s growth. During the experiment, she mated untraumatized female mice with traumatized male mice, separating males from the mothers and offspring to prevent their behavior impacting the offspring. This was repeated for six generations. According to Mansuy, the descendants of the mice showed depressive-like behavior similar to that observed in the separated males.

Likewise, another scientist, Tracy Bale, found biological evidence that trauma can affect sncRNAs in sperm. She also conducted an experiment with mice, stressing them with loud noises and bright light, which caused differences in sncRNAs. She injected sncRNAs from traumatised mice into embryos to see if these behavioural differences persisted. These mice displayed low levels of corticosterone (the mouse equivalent of cortisol), a hormone involved in the stress response. This showed that changes to the DNA with sncRNAs do cause a behavioral difference in progenies, specifically stress.

These experiments show that stress might be inherited in animals, but does this process occur in humans?

Some articles suggest people who experienced racial discrimination have epigenetic changes that affect factors such as schizophrenia, bipolar order, and asthma. Similarly, a study conducted in 2015 highlights that children of Holocaust survivors displayed epigenetic changes influencing cortisol levels. However, the study was criticized due to its small control group and short duration, as it should have been carried out in several generations. Furthermore, the effects might be due to parental and social relationships rather than epigenetics.

Whilst more research needs to be done, and the current studies do not conclude that trauma and stress are inheritable, the social consequences of epigenetic inheritance could be huge. It could change how people think about how their lives are transformed by their progenitor’s experience. Maybe we would even  change our current lifestyles if we knew that our experiences can affect the lives of our children.

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