Research — 02 March 2018

Epigenetics is the latest scientific theory that believes that the trauma we suffer can be passed on to our children on a biological level.

It is interesting how much difference having children makes in your life. Suddenly your savings don’t go on a holiday, but are spent on a down payment on a house. Instead of working late and partying hard, you become fixated on the hours of sleep you can muster. And where a love interest in the past had to be good in bed and have a sense of humour, now you rate them according to their staying power and willingness to share the load.

You start to, often painfully, realise that what you do has consequences for the next generation.

Your excessive drinking risks your daughter choosing a future partner who does the same. If you are an absent father, so might they be. But, of course, if you sing and read to them and surround them with love, they’ve got a good chance of taking that into their futures too. So what we do now often determines, or at least influences, what happens to the next generation. That is scary enough when we can choose our behaviour and, if necessary, change it. But what if we can’t? What if what happens to us alters the way our DNA functions? This week and the next I will introduce you to epigenetics, the new black of (neuro)biology. Next time: more about how the body of our children changes because of what happens to ours. This time: mental health, and how our trauma can surface in the lives of our children, and they become literally part of history.

According to UNICEF, there are more than 50 million uprooted children in the world. They have left their homes because of war, poverty, climate change, discrimination, violence, trafficking or abuse. One way or another they end up living in a country that isn’t theirs. Often they have to learn a different language, adjust to different cultural, religious and economic practices. Sometimes they are on their own. But even if they are treated with love and respect and are given everything they want and need, we know that displacement, especially forced displacement, is a recipe for trauma. That is problematic enough for the people themselves. But now new evidence is starting to emerge that shows that trauma in parents can manifest in their children, and sometimes their grandchildren, as well. And not because the trauma has seeped into the way they parent. But because it has literally changed their children’s biological make-up.

A few months ago, a study by Swedish and Finnish researchers was published that looked at what had happened to the children of people who had been evacuated during WWII. These people were then children themselves, who lived in Finland, but were sent to live in (neutral) Sweden because of the war. The evacuation was well organised and relatively short (two to five years), but a fair amount of the evacuees were left with PTSD or other mental illnesses afterwards. So much so that a percentage of them ended up in psychiatric hospitals. The worrying thing that came out of the study was that daughters of women who had been evacuated were four times more likely to end up with the same problems. And then it started to become interesting. Because there was no such risk for women whose fathers had been evacuated, or for the sons. That is how the academics knew, or at least suspected, that the intergenerational trauma had not been caused by parents telling horrible stories about their childhood, or treating their children in a different way than other, non-traumatised, parents. If it had been nurture, they said, the boys should have been affected too. So in their conclusion, they threw up another possible explanation: epigenetic change in the mothers, which had caused an epigenetic change in the daughters.

“Normal” gene mutations take too long and sometimes we can’t wait for evolution. What helps you cope in stressful situations can be detrimental but it is great that we can adapt, at critical periods, to exceptional circumstances.

Let me explain this as well as my non-beta brain allows. Even as an unfertilised egg you share a cellular environment with your mother and grandmother. When your grandmother was pregnant with your mother, the precursor cell of the egg you developed from was already present in your mother’s ovaries. So what happened to your grandmother when she has pregnant influenced your mother and therefore yourself. And a recent study in mice shows that stress in early life alters the sperm as well. In 2014, academics in Switzerland separated mother mice from their pups and exposed them to stress. Male pups especially soon showed depressive behaviour. And so did their offspring. And their offspring. To rule out the social transmission, the researchers collected the RNA (the copy from the DNA) from the sperm and injected it into freshly fertilised eggs from untraumatised mice. Soon the resulting mice got depressed, and gave birth to more depressed mice.

Neurobiologists are now trying to explain this through epigenetics. Epigenetics is a system that “turns our genes on and off.” If genetics is the computer, then epigenetics is the software. You can’t change your DNA, but you can change the way it functions. That process works through chemical signals in the cells, known as epigenetic tags. They attach to the DNA and tell the cell to either activate or deactivate a specific gene. The most common tag is DNA methylation, a process that blocks proteins from attaching to a gene. As a result, the gene is turned off. When a trauma occurs, DNA methylation can be transmitted, along with a predisposition for problems, to the next generation, and sometimes the generation after that. This is because one of the genes affected by stress is a hormone called cortisol. Survivors of trauma often have low levels of an enzyme that breaks down cortisol. Their children, however, have higher than normal levels of the enzyme. The idea is that this is because the enzyme is usually present in high levels in the placenta to protect the fetus from the mother’s cortisol. If the pregnant mother has low levels of the enzyme, the fetus will be exposed to higher levels of cortisol. As a result, it will develop higher levels of the enzyme to protect itself, lowering the cortisol levels. And cortisol is a hormone that is associated with our ability to regulate emotions and manage stress. Low cortisol tends to mean that you are more susceptible to stress-related illnesses. Hence the chance of secondary PTSD, depression or anxiety.

Daughters of women who had been evacuated were four times more likely to end up with the same problems. The intergenerational trauma had not been caused by parents telling horrible stories about their childhood…

Since researchers have started to understand epigenetics better, there have been more and more studies that deal with its consequences. One of the most famous was done by Rachel Yehuda, a professor of psychiatry and neuroscience in New York. She looked at the levels of cortisol in Holocaust survivors and their children and found that children of parents who had PTSD as a result of the Holocaust were born with low cortisol levels similar to their parents. In fact, if a parent had PTSD, the children were three times more likely to suffer from PTSD, anxiety or depression themselves. Since then, Yehuda has done research into mothers who were in the second or third trimester while they were involved in 9/11. Again, if the result of that was PTSD, these mothers gave birth to babies with low cortisol levels. They were also smaller. Other researchers think that epigenetics plays a role, but is mitigated by parenting. For instance, academics at Imperial College London followed 125 mothers and their children from pregnancy through to 17 months postnatal. If there were cortisol problems with the mothers, that negatively predicted cognitive ability in the babies. But they also saw that if the mother and the child had a close relationship, the impact of those negative factors were far less than if mother and child had trouble bonding.

And that is the good news and a counterpoint to the critics, who say that epigenetics is a form of what they call “neuro-determinism”, a fatalistic idea that we are nothing but machines, incapable of change, let alone free will.

First of all, as Yehuda says, the changes occur to help the children cope better with the circumstances that stressed out the parents. “Normal” gene mutations take too long and sometimes we can’t wait for evolution. The problem is that what helps you cope in stressful situations can be detrimental when life goes back to normal. But it is great that we can adapt, at critical periods, to exceptional circumstances. That helps the child in question, and the human race in general, to survive. Of course, that doesn’t help the children suffering from secondary PTSD. And it is also not something that we can tell the 50 million refugee children who might become their parents. What is a positive message, is that our growing knowledge of our “plastic” gene settings can help solve some of the problems. Knowledge is power and scientists are already looking at medication, diet, therapy and other ways to fix a number of the issues. Maybe, if we can figure out how to do that, we can prevent a lot of unhappiness and suffering, and do something to halt at least part of the current mental health epidemic.

This piece by  was first seen on ‘The Big Smoke Australia‘, 26 February. 


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