During a date this year, the simple conversation of fears sprung up. We discussed our “shallow” fears, such as my childish fear of insects and the dark, but also more “complex” fears like dying. As a David Attenborough enthusiast growing up I used to be fond, even fascinated, by insects but over the last few years I have developed a catastrophic fear of bugs. So, where did this fear come from? Do we need to experience trauma to have fears? Or can these fears be inherited from our parents? This topic is a hotspot in neuroscience and I am hoping to do clinical research about how trauma affects our brain. Albeit, let’s start with our genetics.
Epigenetics is the study of heritable changes in gene expressions, but it does not involve changes to the underlying DNA sequence. Is the phrase “scarred for life” scientifically possible? Studies have shown that traumatic experiences in your life can create permanent marks on your DNA- thus altering it. This makes it very possible to potentially pass your fears to your children.
Fear causes a “fight or flight” response. It heightens your stress levels and neuronal activity in the hypothalamus and amygdala. The amygdala belongs to the temporal lobe and is thought to be the control centre of your emotions and tunes your perception of these emotions in others. Depending on the severity of the trigger, trauma can cause abnormal and neurodivergent brain activity such as anxiety, depression and/or PTSD. These disorders have been associated with epigenetic mechanisms. Learning and Memory published an article, the author states “Stress elicits both immediate and long-lasting psychological, physical, and emotional strain on an individual, leading to profound neurobiological changes that impact future behavioral responses. Animal models of stress exposure have identified epigenetic modifications in key brain areas known to be critical components of the circuitry responsible for both the expression of anxiety and formation and expression of fear memories, such as the frontal cortex, hippocampus, and amygdala”
Fear is essential for survival. A scared mouse is better than a dead mouse, but where do we draw the line? Do you fear something or are you traumatised by it? Epigenetics does not change the DNA sequence but leaves markers on the genes. These changes turn certain genes on or off that dictate cell function. In a study performed at Emory University in 2014, researchers used fear conditioning to investigate the effect it had on future generations. The study conditioned male mice to fear a acetophenone (a scent) by exposing them to the smell before introducing small electric shocks. The animals obviously soon learned to associate the smell with the pain from the electric shock and exhibited fear responses even without the electroshock. (A bit like Pavlov’s experiment). This response was passed down the mice’s lineage, despite those generations never being exposed to the electroshock. The scientist's claim that low DNA Methylation levels on the genes responsible for sensing the odour is the reason. A 2015 study led by Rachel Yehuda proved how children of holocaust survivors had an increased likelihood of developing stress disorders, assigning this to ‘Holocaust exposure’. Genetically, the survivors and their children possessed the same chemical tags on the same gene and these tags were absent from the control group. C Marcus Pembrey of UCL: epigenetics is “the very beginnings of an understanding of how one generation responds to the experiences of the previous generation. It’s fine-tuning the way your genes respond to the world.”
I have included the mechanism of DNA modification through DNA methylation and histone modification^ which you absolutely don't need to know or understand, unless you are on my course...
It would be ignorant of me to not discuss or even make you aware of the effect race has on epigenetics. African-Americans disproportionately experience more severe and debilitating chronic pain than non-Hispanic Whites. These differences are thought to be due to differential exposure to psychosocial and environmental factors, including adverse childhood experiences, racial discrimination, low socioeconomic status, and depression, all of these factors have been associated with chronic stress and chronic pain. Economic hardship, racial trauma and childhood stress can affect gene expression without altering the underlying genetic sequence. The trauma of slavery is something that is literally embedded in the genetics of black people. On the other side of the coin, could the brutality of white slave owners be something that may have been passed down to their children? I aim to revisit this topic of fear and epigenetics in much more detail in the future, as I develop my own knowledge on this phenomena.
Hopefully, the takeaway question for you is:
Are our “irrational” fears the fears of our ancestors?
- sham
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