In 1966, psychologists noticed something interesting. Proportionally, more grandchildren of Holocaust survivors sought mental help in Canadian clinics compared to the rest of the population. Mounting evidence show that descendants of people who have experienced trauma like the Holocaust are at greater risk of anxiety, depression, posttraumatic stress disorder, and other conditions.
But while studies show that significant trauma can alter certain brain processes, we aren’t so sure if these changes are genetic. We know trauma is somehow passed onto the next generation. But is it more based on nature or nurture?
Nature vs Nurture
It’s the classic debate. And on the topic of intergenerational trauma, scientists have picked sides. They’ve suggested and argued about multiple theories, two of which are epigenetic transmission and parenting methods.
The “nature” theory
The epigenetic transmission theory is the idea that trauma causes epigenetic changes in the DNA, which the next generation inherits. Epigenetic changes means that your body activates some genes and deactivates others. It’s a normal process that starts from our development in the womb and continues throughout our lives. For example, as you grow up, epigenetics help your stem cells develop into different types. Certain genes are turned on or off depending on the type of cell being created. For a stem cell to become a skin cell, epigenetics turn on genes that instruct it to create skin cell proteins.
The study that sparked the theory examines the DNA of children who survived the Dutch Hunger Winter famine in the womb. Interestingly, researchers found a unique chemical mark called an epigenetic signature on one of their genes. Further analysis found that having that chemical mark led to having higher body mass. It does seem to me that the epigenetic signature was some sort of survival response from the famine. It’s almost like the body, sensing some shortage of food, activated a gene to conserve more nutrition in the future. Of course, with the famine gone, conserving more nutrition than others may have led to higher body mass.
The “nurture” theory
Parenting methods, on the other hand, is a more environmental and psychological explanation for intergenerational trauma. Clinical psychologist Yael Danieli analyzed over 400 descendants of Holocaust survivors in a study in 2016, identifying “adaptational styles” their parents developed to cope with trauma. Danieli separated these adaptational styles into three categories (victim, numb, and fighter), as well as investigated the impacts each had on the children of survivors. The study describes some survivors developing strict parenting styles, and others not expressing love or warmth. Another study conducted by Brent Bezo on survivors of the Holodomor genocide noticed that these parenting styles can pass on to future generations.
So which is it?
Critics of the epigenetic transmission theory say that there isn’t enough evidence to support their hypothesis. There hasn’t been a clear explanation of how epigenetic transmission works in humans. Some, like John M. Greally, professor at the Albert Einstein College of Medicine, have said that “too much causality is claimed”. Other studies involving mice and even humans have delivered evidence in support of the heritability of trauma, but there are still many questions that need to be answered.
The parenting explanation is more plausible, but I think it’s very likely that it isn’t the only reason for intergenerational trauma. While relatively new, the field of epigenetics offers some very promising answers to the current mystery. It also has the potential to revolutionize psychiatry and therapy. If we understand how trauma passes on, we can develop better ways of helping those who are at risk.