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The stress of our fathers

by Dr. Claudia Aguirre

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The convention in psychology is that there are two ways our behavior is influenced: we inherit it genetically (nature) or we learn or acquire characteristics based on our upbringing (nurture). That’s a very black and white view, in my opinion. So where’s the grey area in this seesaw between our genes and the environment?

Enter epigenetics. Epigenetic modifications alter the expression of genes, but not their actual DNA sequence. For instance, children conceived during wartime famine have an increased risk of diabetes, heart disease and other conditions — possibly because of the stress and hunger their mothers experienced, and not necessarily because heart disease runs in their family. In other words, epigenetics can explain how we inherit the environment.

How does it work?

The environment can alter genetic function due to a relationship between DNA strands and the proteins they wrap around. Think of DNA like the strings on a guitar. These strings are bound in place by pegs which turn and tune the string to a particular pitch. The tighter they’re wound, the higher the pitch. Our genes work in a similar way, except the tighter the DNA is wound, the harder it becomes for it to make its end-products. Methyl groups, in particular, attach themselves to DNA and turn the peg to make the string tighter. Stress and anxiety can clamp methyl groups onto DNA, turning the pegs to make the strands tighter and inhibiting DNA function. Talk about feeling wound-up. Other molecules, called acetyl groups, play the opposite role, unwinding DNA around the peg. In music you just the right turn on a tuning peg – not too much or too little – to hit the right note. The same goes for DNA’s ability to function properly.

Nature’s Nurture

Recent science suggests that we may also inherit out-of-tune DNA strands. A landmark paper, “Epigenetic programming by maternal behavior,” was published in June 2004 in the journal Nature Neuroscience. In a series of studies, neuroscientists showed that a mother’s care (in rats) was the determining factor in how the rat pups grew up. Lousy moms reared pups that grew up to be stressed and anxious adults. However, when pups born to lousy moms were adopted by caring ones, they grew up to be healthy. And when the stressed out pups were given a drug that wiped out methyl groups, despite being neglected and abused, they developed perfectly normal adult brains and behaved socially. These and other studies show that our behavior is not set in stone by our genes. It is malleable and the right intervention can have lasting effects.

A more recent animal study showed that this behavioral inheritance can transpire through generations. Rat dads exposed to a particular scent that was paired with a frightening experience learned to be fearful of the scent. Fair enough – we’ve seen that before. But then the scientists looked at the grandkids of these rats and found they, too, were fearful of the scents despite having never smelled them in their own lives. How is this possible? Does our own stress and anxiety stem from our grandmother’s stressful experience? Holocaust survivor studies point to yes, but much more research is needed to understand this gray area between our genes and our environment.

A Way Out

Understanding that even our genetic function is not set in stone is incredibly liberating. Even as adults, we can modify our brain in ways that affect our behavior. Take meditation, for example. Neuroscientist Richard Davidson and his group found that expert meditators had reduced levels of the genes that remove acetyl groups. (Remember the ones that loosen up the strands?) So perhaps meditation changes us not only at the genetic level, but also at the epigenetic level. While we’re only scratching the surface of how mind-body therapies work, we know that keeping stress levels low is as important as human connection through touch. And both are especially important during motherhood. Stress suppresses maternal behavior, and maternal behavior, through touch, fosters healthy offspring. So don’t worry so much about whether you’re doing the right or wrong thing all the time. A simple caress is an easy way to turn down the genetic dial for stress – and that’s the best kind of genetic legacy to leave behind.

Dr. Claudia Aguirre

Dr. Claudia Aguirre is a neuroscientist and mind-body expert. She earned her doctorate degree in Neuroscience from the University of Southern California (USC), and she recently completed a year-long certificate course on Mindfulness, Yoga and Social Change from Loyola Marymount University. She is also a TED Ed educator, creating various neuroscience-related lessons, which have reached millions worldwide. She researches the latest science around mindfulness and meditation, and communicates these findings to the Headspace audience.

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