Short Wave - The Legacy of Trauma: Can Experiences Leave A Biological Imprint?

Episode Date: February 25, 2021

Descendants of trauma victims seem to have worse health outcomes. Could epigenetics help explain why? Bianca Jones Marlin and Brian Dias walk us through the field of epigenetics and its potential implications in trauma inheritance. You can follow Ariela Zebede on twitter @arielazebede. Email us at [e-mail] pcm.adswizz.com for information about our collection and use of personal data for sponsorship and to manage your podcast sponsorship preferences.NPR Privacy Policy

You're listening to Shortwave from NPR. It was October of 1944. World War II was almost over and the Allied forces were winning. The Germans retaliated by blocking food supply to the Netherlands. That year, there was an unusually early and brutally cold winter. The Netherlands were completely cut off of food. People there were really, really starving. It was an extreme famine to the point where,

That's Bianca Jones Marlin. She's a postdoctoral fellow at Columbia University. And that time in the Netherlands is now known as the Dutch Hunger Winter. Thousands of people died and thousands more experienced intense starvation. Now, this was a really specific and well-documented moment in time, which made it ripe for investigation. Researchers wanted to try and study the effects of hunger on development. And they found that the children of people who were pre-examined. pregnant during the famine were more likely to have obesity, diabetes, cardiovascular disease,

and they had shorter lifespans too. But what's really surprising is that the grandchildren of people alive during the hunger winter were more likely to have poor health too, meaning those a generation removed from the trauma. Bianca and others are trying to figure out how and why. I look at how trauma or stressors can be passed down through generations and not just how they're passed down through lore or word or storytelling about how they're passed down by being remembered in the cells in our body. It's called epigenetic inheritance of trauma. And this research is pretty new. Bianca is one of a handful of scientists exploring the possibility of this.

So today on the show, we take a look at the field of epigenetics, how our behaviors and environment can change the way our bodies use DNA. And whether those changes might last generations. I'm Ariela Zabidi. And I'm Maddie Safaya. You're listening to Shortwave from NPR. Okay, so we are talking about epigenetics today. Where do we start, Ariel? Well, we got to go back to the basics.

Genetics minus the epipart. So most of the time when we think of genetic changes, we think about DNA mutations. Basically changes in the actual sequence of our DNA. Yeah, and it turns out this isn't the whole story. Our DNA is covered in small molecules. that tell our body how to use the DNA. Brian Dias gave me a great metaphor to describe all this.

He teaches at the University of Southern California's School of Medicine. So within you and I is our Book of Life, which is our DNA, and that DNA needs to be read. And if our DNA is a book of life, then those small molecules I was talking about are the punctuation marks. And depending on what punctuation is put where, the book is going to be read very differently. Meaning those markers can amplify or quiet down certain parts of our DNA.

So when we talk about epigenetics, we're talking about how these molecules around our DNA affect how our DNA is red. Exactly. And we can see this really clearly in different parts of our body. How so? Well, every cell in our body has the same blueprint, the same DNA. But we know that not every cell in our body is the same. We don't have teeth growing in our liver. We don't have eyes growing in our fingertips. I mean, speak for yourself over there.

So look, even though our cells all have the same DNA, the DNA is being used differently in different cells. And I'm guessing epigenetics has something to do with it? Yes, our epigenetic markers vary in different parts of our body. In the eye, for example, there's certain markers that say you become an eye cell and suppress everything that will make you a tooth. And here's the thing.

Our environment and behaviors change our epigenetics all the time. Not enough to make teeth start growing out of your eyes, I promise, but still changing. Yeah, and I remember learning about this discovery in grad school and it being revolutionary. Like, oh, our environment can affect our genetics in real time without actually changing the sequence of our DNA at all. Yeah, and of course it's more complicated than that. But this field is a really big deal. It's shown us that different environmental factors like diet and pollution can change our epigenetic markers. And now people are trying to figure out if trauma and stress also cause epigenetic changes.

And if they do, can these changes be passed down? Like the Dutch hunger study we talked about earlier, right? Yeah, among others. Now look, we can't assume too much from these human studies. They have small sample sizes. There are tons of confounding variables. Right, right. I mean, isn't it possible, Ariela, that these descendants are more likely to have these diseases due to social factors?

Yes, and I asked Bianca the same question. She said, for sure, that's a problem with human studies. It's really hard to separate the learned experience from the biological one. It is hard to say that a parent who was starred will now then treat food in the same way as a parent who is not starved. And what we're interested in looking at is if we remove the parent from the situation and we just have, the sperm cells and the egg cells, do all the work. Do we still see these changes? And one way to start to figure that out is by doing animal studies.

Right. So Brian, the scientist who gave us that cool metaphor earlier, did some of the first groundbreaking research on this. He basically introduced male mice to a particular smell. And when we expose the mice to a smell, we administer a very mild foot shock that we first test on ourselves and we know is not painful, but mildly annoying to the mouse. And as a consequence, that particular smell becomes stressful to the parental generation.

And what happened was that these scared mice had different epigenetic markers around a smell receptor gene in their sperm cells. So when they bred those mice with females... What we find when we look at the noses of those offspring is that those nose, noses now have more receptors that would respond to the smell that the fathers had been made stressful to. Their noses, the offspring noses, were devoting more real estate, more cells to processing that particular smell. And these offspring mice were extremely sensitive to the smell. Wild.

And look, you could say, okay, maybe the mouse was anxious and that anxiety rubbed off on his kids. Maybe it was a social thing. Right, right. To get around that, Ryan took the father mouse out of the equation. He took the sperm from the scared males and fertilized the eggs artificially. That way, the dad wasn't interacting with the baby mice or even with the mom, and you could rule out any learn changes. And were these baby mice still more sensitive to the smell, even with the father kind of removed? Yes, which suggests that it actually was being biologically inherited.

Something that's being contained in the sperm that's allowing for these effects to actually perpetuate across generations. Okay, so let me make sure I have this right. So we've seen in mice that fear or trauma or stress, whatever you want to call it, might be epigenetically inherited. I mean, what does that mean for humans? Yeah, well, like I said, this science is really new. We're still just learning about how epigenetic changes might be inherited at all. So we can't make any big conclusions just yet. But the evidence that we do have at least opens a whole box of questions about how trauma can affect our health.

Here's Bianca again. How does a trauma and a parent live on when you're a third grader trying to pay attention in the classroom? Or you're someone who's new on the job and suffers from extreme anxiety. Or you're someone who can't seem to maintain healthy relationships because of traumas that you've had in the past. Or you can't sleep at night. Yeah, and I feel like this is especially important right now, right? I mean, we're reckoning with health disparities and how COVID disproportionately affects many minoritized communities. Yeah, Bianca says the same thing.

We know that in Native American populations and black American populations, the numbers associated with diabetes and hypertension are extremely high. And these are two populations, specifically black American population that have been starved for generations upon generations upon generations and stressed upon generations upon generations. upon generations. And we see the ramifications in health, but A, it's hard to separate that from racist institutions, and it's also hard to separate that from modern-day trauma. There are tons of reasons for contemporary health disparities. And Bianca hopes that her research can help us think about the effects of trauma differently. When we can figure out the molecular mechanism and say, here in the brain, these changes are occurring, here on the epigenome, these changes are occurring, this has to be seen as a health crisis.

because we have the data that supports that. In a similar way that there's markers for cancer, there's markers for trauma. And at first glance, these markers tell a sad story, right? They say that people might be suffering because of things that their parents or grandparents experienced. But every researcher I spoke to said that the beauty of epigenetics is that it's not as set in stone as our DNA. That means if we can put a marker on, potentially a marker can be removed. that through living in a healthy environment with love and safety, we can change these markers.

If these markers can be put in, there's potential that these markers can be taken away. All right, Aureel Zabidi, thank you for bringing this on the show. We appreciate you. Thanks for having me, Maddie. This episode was produced by Britt Hansen. Fact-checked by Burley McCoy and edited by Viet Le.

The audio engineer for this episode was Daniel Shukin. I'm Maddie Safia. And I'm Ariel Zabidi. Thanks for listening. to shortwave from NPR. When the survivors of a mass shooting at a newspaper went back to work, everything was different, even email. What if someone's sending us more death threats or what if somebody sends me a death threat and I don't

see it? And then somebody comes and kills all my friends and it's my fault because I didn't read the email. That's this week on the Capital Gazette series from NPR's Embedded.