Here is the third and final installment from Chapter 2 of Mark Wolynn’s book It Didn’t Start With You which concludes his coverage of genetic research shedding light on how stress and trauma are passed on through at least three generations :
It’s only recently that scientists have begun to understand the biological processes that occur when trauma is inherited. To learn more, researchers turned to animal studies….Chemical changes in the blood, brain, ova and sperm of mice are now being linked to behavioural patterns, such as anxiety and depression, in later generations. Studies performed on offspring, for example, have shown that trauma, such as the stress of maternal separation, caused gene expression changes that can be traced for three generations.
In one such study, researchers prevented females from nurturing their pups for up to three hours a day during the first two weeks of life. Later in life, their offspring exhibited behaviors similar to what we call depression in humans. The symptoms seemed to worsen as the mice age. Surprisingly, some of the males did not express the behavior themselves, but appeared to epigenetically transmit the behavioral changes to their female offspring. The researchers also discovered altered methylation and gene expression changes in the stressed mice. Among the genes involved was the CRF2 gene, which regulates anxiety in both mice and humans. The researchers also found that the germs cells – the precursor egg and sperm cells – as well as the brains of the offspring were affected by the stress of being separated from their mothers. In another experiment….offspring that received low levels of maternal care were more anxious and more reactive to stress in adulthood than were the rats that received high levels of maternal care. The stress pattern was observed in multiple generations.
It’s common knowledge that infants who have been separated from their mothers can experience challenges as a result. In studies involving male mice, pups that were separated from their mothers exhibited lifelong increases in stress susceptibility and generated offpsring that exhibited similar stress patterns over several generations. (In one study).. conducted at the Brain Research Institute of the University of Zurich in 2014, researchers subjected male mice to repeated and prolonged periods of increased stress by separating them from their mothers. Afterward, the traumatised mice exhibited a number of depression like symptoms. The researchers then had the mice reproduce and discovered that pups in the second and third generation showed the same symptoms of trauma despite never having experienced it themselves.
(Similarly)…. high numbers of microRNA – genetic material that regulate gene expression – (were) present in the sperm, blood and hippocampi of the traumatised mice..(and)…in those of the second generation……Although mice in the third generation expressed the same symptoms of trauma as did their fathers and grandfathers. elevated numbers of microRNA were not detected.
In a later study published in 2016, Mansuy and her colleagues were able to show that trauma symptoms could be reversed in the mice after they lived in a positive, low stress environment as adults. Not only did the mice’s behaviors improve, they also experienced changes in DNA methylation, which prevented symptoms from being passed to the next generation. The implications of this study are particularly significant. In later chapters we’ll learn how to create positive images and enriching experiences that can help reverse stress patterns that may have affected our family for multiple generations.
What makes the mouse research so intriguing is that science can now substantiate how the challenges experienced in one generation can become the legacy transmitted to the next. In a study involving the offspring of stressed male mice conduucted at Emory University School of Medicine in 2013, researchers discovered that traumatic memories could be passed own to subsequent generations throgh epigentic changes that occur in DNA. Mice in one generation were trained to fear a cherry blossom-like scent.. Each time they were exposed to the smell they simultaneously received an electric shock. After a while, the shocked mice had a greater amount of small receptors associated with that particular scent, enabling them to detect it at lower concentrations. They also had enlarged brain areas devoted to those receptors. Researchers were also able to identify changes in the mice’s sperm.
The most intriguing aspect of the study is what occured in the next two generations. Both the pups and the grandpups, when exposed to the blossom odour, became jumpy and avoided it, despite never having experienced it before. They also exhibited the same brain changes. The mice appeared to inherit not only the sensitivity to the scent, but also the fear response associated with it.
Brian Dias, one of the researchers of the study, suggests that “there’s something in the sperm that is informing or allowing that information to be inherited.” He and his team noted abornmally low DNA methylation in both the sperm of the father mice and the sperm of the offspring. Although the exact mechanism for how a parent’s traumatic experience gets stored in the DNA is still under investigation. Dias says, “it behooves ancestors to inform their offspring that a particular environment was a negative environment for them.”
Ths particular study provides compelling evidence for what the researchers term “transgenerational epigenetic inheritance,” the notion that behaviours can pass from one generation to another. When I work with families in my pratice, I often see recurring patterns of illness, depression, anxiety, relationship struggles, and financial hardship, and always feel compelled to look deeper. What unexplored event in a previous generation drives the behavior of the man who loses all his money at the racetrack, or the woman who chooses to be intimate only with married men? How have their genetic inheritances been influences?
Given that a generation in humans is approximately twenty years, the results from human studies spanning multiple generations are still pending. However, with the research demonstrating that stress can be transmitted through at least three generations of mice, the researchers surmise that children born to human parents who experienced a traumatic or stressful event would also likely pass the pattern down not only to their children, but to their grandchildren as well. Uncannily the Bible in numbers 14-18, appears to corroborate the claims of modern science – or vice versa – that the sins, iniquities, or consequences of the parents can affect the children up to the third and fourth generations. Specificially, the New Living translation states : “the LORD is slow to anger and filed with unfailing love, forgiving every kind of sin and rebellion. But he does not excuse the guilty. He lays the sins of the parents upon their children; the entire family is affected – even children in the third and fourth generations.”
As new discoveries in epigentics are revealed, new information about how to mitigate the transgenerational effects of trauma could become standard practice. Researchers are now finding that our thoughts, inner images and daily practices, such as visualisation and meditation can change the way our genes express, an idea we will examine in more detail in the next chapter.
The idea that we relive family traumas may well be at the core of what psychiatrist Norman Doidge alludes to in his breakthrough book he Brain That Changes Itself when he writes “Psychotherapy is about about turning our ghosts into ancestors.” By identifying the source of our generationl traumas Dr. Doidge suggests that our ghosts can “go from haunting us to become part of our history.”
To be continued