Shinjini Bandopadhyay, Amity University Kolkata
Adverse childhood experiences (such as early life adversity, stress, and childhood trauma) can have a lifelong impact on mental and physical health.
Childhood trauma has been associated with post-traumatic stress disorder (PTSD), anxiety, depression, bipolar disorder, diabetes, and cardiovascular disease that manifest later on in adult life.
Most or all of these traits have also been found to be exhibited by the children of individuals affected by severe psychological trauma at some stage in their lives. This article explains how epigenetic modifications may mediate the transmission of trauma from parent to offspring.
The heritability of conditions such as PTSD, depression, etc. is very variable for a given phenotype implying that gene/environment interactions (such as through epigenetic modifications) may be involved in the onset of these phenotypes.
EPIGENETIC MODIFICATIONS
Each cell in the living organism, under normal conditions, shares the same copy of DNA, but eventually develops and differentiates to different cell types due to instructions provided by epigenetic modifications. Epigenetic regulation can occur throughout the lifespan and can be induced by random changes or by multiple different environmental factors.
Epigenetics regulates the ‘turning on or off’ of genes without changing the DNA sequence, but instead affecting the accessibility of regulatory transcription factors to the gene for its expression. Epigenetic modifications include DNA methylation, histone modifications, and various RNA-mediated processes.
The most common one is DNA methylation i.e. the attachment of methyl groups to specific nucleotides in the DNA molecule. When methyl groups are attached to the promoter, they typically suppress gene expression.
Changes in the human epigenome have been associated with the processes of adaptation and evolution. Epigenomic alterations are also associated with pathologies characterized by behavioral or/and cognitive problems, as well as with illnesses characterized by childhood trauma exposures, such as mental disorders.
THE EPIGENETICS OF TRAUMA
Early life is a vital period characterized by a high level of plasticity and fast development. Thus, the impact of childhood trauma is particularly serious since the developmental trajectory of the brain is affected, with resultant alteration of the neural circuit for threat detection and emotional regulation.
Changes in gene due methylation of DNA is associated with several psychiatric dysfunction. For instance, an association between DNA methylation and both depression and suicide has been discovered.
The hypermethylation of tyrosine receptor kinase B (a receptor protein for brain-derived neurotrophic factor or BDNF which is important for nervous system development) was especially involved in suicide. There are also epigenetic changes associated with PTSD.
Some people seem to develop PTSD after experiencing trauma, while others do not. A possible explanation could be an underlying genetic or epigenetic risk in those who are more prone to develop PTSD or a protective epigenetic make-up.
Epigenetics could offer insights into differential susceptibility to the risks of developing psychopathology.
INHERITING TRAUMA FROM PARENTS
Evidence suggests that there is some transgenerational transmission of psychological trauma from parents to children. Transgenerational epigenetic transmission is defined as the transmission of genomic information from one generation to the next without changing the main structure of DNA.
It is hypothesized that trauma-induced epigenetic modifications (such as DNA-methylation) can be passed from traumatized individuals to subsequent generations of offspring.
Children of parents who had suffered from extreme trauma exhibit methylation modifications which are associated with trauma and PTSD. This may support the combined influence of not only environmental trauma but also of the biological component of PTSD risk.
Many studies found that the glucocorticoid receptor (NR3C1) gene for glucocorticoids (stress hormones) is associated with methylation changes. For instance, maternal exposure to intimate partner violence during pregnancy has been associated with increased NR3C1 DNA methylation in teenage children.
Maternal exposure to war violence or rape during pregnancy was also associated with increased methylation in the NR3C1 promoter region in new-borns. Different factors influence the passing on of such trauma, especially the timing: whether it occurred before pregnancy or during pregnancy.
This increased methylation of the NR3C1 gene could increase stress reactivity and have a long-lasting effect on the vulnerability to stress, trauma, and chronic disease development.
Maternal stress is also seen to be correlated with low birth weight; mothers exposed to genocide trauma were also seen to have children with significantly higher levels of PTSD and depression later on.
Sometimes the effect on offspring may be contradictory; it was seen that in Holocaust survivors who suffered extreme starvation (which is another environmental factor that can affect the epigenome) their offspring were more prone to metabolic syndrome. Although this is a surprising find, one possibility is that it may be a compensatory mechanism.
There is increasing evidence and studies suggesting the transgenerational transmission of epigenetic changes from parents to children as an explanation behind the onset of various mental and physical disorders stemming from trauma.
Also read:Insulin treatment associated with mortality in patients with COVID-19 and Type 2 diabetes
REFERENCES
- Nagy A. Youssef, Laura Lockwood, Shaoyong Su, et al; The Effects of Trauma, with or without PTSD, on the Transgenerational DNA Methylation Alterations in Human Offsprings; 2018; Brain sciences; Vol: 8(5):83; DOI: 10.3390/brainsci8050083
- Shui Jiang, Kynne Postovit, Annamaria Cattaneo, et al; Epigenetic Modifications in Stress Response Genes Associated With Childhood Trauma; 2019; Frontiers in psychiatry; Vol: 10:808; DOI: https://doi.org/10.3389/fpsyt.2019.00808
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Great article!