Intrusive thoughts during pregnancy, paternity detectives, and updates from the Trump Tracker
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This is a science podcast for March 7th, 2025. I'm Sarah Crespi. First this week, international news editor David Malakoff joins me to talk about the most recent developments in U.S. science under the new administration. After that, we have contributing correspondent Andrew Curry. We're going to talk about researchers looking into the question of how often children are genetically unrelated to their presumed fathers using genealogy and genetic testing.

Finally, researcher Suzanne Schweitzer discusses intrusive thoughts in the perinatal period as part of a special issue on women's health in Science Advances. Almost all pregnant people and recent mothers experience intrusive thoughts about harm coming to their offspring. Schweitzer and colleagues suggest that gaining a better understanding of intrusive thoughts during this highly predictable window could help explain the phenomenon more broadly.

As the Science News team tries to keep up with the daily changes to the scientific enterprise in the United States, we here on the podcast are lucky to catch a reporter and editor once a week to give us the download. Right now it's Tuesday, March 4th. The podcast will go live Thursday, March 6th. And we have David Malakoff. He is helping manage all the coverage that we're doing of the administration. Hi, David. Welcome back to the podcast. Hey, Sarah. Good to be here.

Yeah, there is so much going on. I think we'll go through it agency by agency, starting with NIH, the biggest scientific funder in the world. Yeah, you know, so NIH accounts for about half of all the civilian research spending in the United States. So it's very important to the research community. And we've got a lot going on there. One thing we wrote about recently is the plight of what are called Title 42 employees, who

The name comes from a statute, and that statute allows the federal government to hire people at pay rates that are higher than the typical federal pay scale. The reason that's allowed is to enable agencies to hire a really exceptional talent and bring them to the agency. NIH is one of the agencies that has this capability. They've used their Title 42 authority to hire about 4,000 senior scientists across the agency.

But those scientists, typically about 80% of them are on fixed terms. So they serve terms of one to four years. And traditionally, those terms have been renewed with little question for most of them. But in this case, the Trump administration has said that they are not going to renew those terms as they come up. So as a result, scientists learned that at least 30 and possibly more than 100 of these senior scientists at NIH

are now faced with losing their jobs. They left perhaps a lab, a company, an industry job in order to work for the government. And yeah, there is some money, but it is not an exceptional paycheck. Right. Relative to what they could earn in private industry or often in academia, you know, it's competitive. And yeah, they often gave up tenured positions and very well-funded labs.

to come to NIH because NIH, the intramural program, NIH has the extramural program, which gives about $39 billion to scientists outside the agency. But then it's got an intramural program, which is about $6 billion, which supports labs at the NIH campus in Bethesda, Maryland, and also a very extensive clinical center where they treat patients. Title 42 employees are sort of disproportionately gathered in that intramural program. So this would have a

big, big potential impact on that intramural program. Yeah. So on the plus side, NIH has restarted some of these meetings that were canceled during the communications pause, but some of these meetings are resuming to what, review grants?

Yeah, Monday morning, we saw in a publication called the Federal Register, which is sort of the government handbook of what's happening every day. And to hold a meeting, most agencies have to post a notice in the Federal Register 15 days in advance or sometimes 35 days in advance, telling the public that this meeting is happening. NIH had been banned from

from placing those federal register notices. So it had had to cancel many of the meetings where grant proposals are reviewed or new grants are approved. So it had really put sand in the gears of the whole grant making process. Now we're seeing that at least some of those meetings are being rescheduled. They're getting their federal register notices. And so those meetings have restarted at this point.

But not all of them. About a quarter of those meetings are held by the individual institutes at NIH. So far, those institutes currently are still not allowed to place those Federal Register notices. And how has the granting rate been? This is another story that has come out in the past week. Yeah, it's at a reduced rate what people have tried to take a look at this. You can sort of track how much money flows out of NIH over a given time period.

And what people are seeing is that in the early part of this administration, the amount of money moving out the door is less than moved out the door, say, at a similar period a year ago or two years ago. And we know that's because...

These meetings aren't being held, but they're also canceling grants? Yes. So that's been another piece of this, which is NIH is proactively canceling grants that they have already awarded. We know, for example, that they have canceled grants regarding research involving transgender individuals. That's been one target.

There have been other kinds of grants dealing with diversity, equity, and inclusion that appear to have been targeted. The transparency is still lacking. We don't know exactly what's always going on. And often we don't learn about a cancellation until the researcher who had that grant goes public and says, yeah, my grant has been canceled. Sometimes they don't go public because they are trying to appeal and change that decision. Yeah. And so...

There is also a court case that might actually influence what happens with funding from NIH as well. This relates to the indirect costs, not necessarily a grant being canceled, but parts of grants that are supposed to fund the infrastructure surrounding laboratories. That's right, Sarah. Yet another issue. A few weeks ago, NIH abruptly came out late on a Friday night with a new policy regarding these overhead grants.

This is money that universities and other research institutions get to support administrative costs or facilities. So let's say you get a hundred thousand dollar grant. You might get an additional $50,000 to cover keeping the lights on and doing the administration and all the regulatory work that needs to be done. Uh,

What NIH said is that they are going to cap those overhead costs in such a way that basically would reduce them very substantially by about $4 billion a year. Not surprisingly, research institutions were very, very concerned about that. Among other things, for example, those overhead costs support these very large research animal facilities where you might have tens of thousands of mice or hundreds of primates, and

And those facilities are suddenly worried, well, we may have to euthanize a lot of these animals if we don't have that overhead cost money to support these. So a judge issued a temporary ban very quickly. The policy came out on a Friday. By Monday, a judge had said, wait a second, NIH, I'm not sure this is legal, the way you're doing this. So they put a pause on it. That judge is now determining whether that pause is going to be extended further.

We might get that decision this week, probably no later than Monday of next week. And that could also be appealed further up. Absolutely. Yeah. Okay. So let's go to NSF. So this is the National Science Foundation, which also funds a lot of

Research in the physical sciences. What's happening there? Right. So NSF is essentially the major funder of non-biomedical research. It's, you know, seven, eight plus billion dollars a year. So the big news that came out there this week is that the agency rehired 84 probationary employees that had just fired. And the reason they did that is because, again, another federal judge rehired

ruled that the way these firings were carried out was illegal.

And so NSF appears to have interpreted that ruling to mean that they have to reinstate these employees. There were about 85 odd of them and they reinstated most of them. However, they did not reinstate another group of 80 odd employees who were what were called sort of temporary experts that the agency brings in. Those firings remain in place. Does that mean that the way NSF did it is different than the way

NIH did it, or we've seen at NOAA, there are all these firings of probationary employees. Are they doing something different, or did they just not go to the same judge? Yeah. So this gets into the complexities of federal hiring and firing rules. In this case, what happened was a union went to court and said, at a number of agencies, the Office of Personnel Management, which is the federal agency that

handles human resources, that OPM told the agencies to fire these people. And the union argued that OPM does not have the authority to hire and fire people. Only the agencies and departments have that authority. And so in these cases, they argued the departments and agencies had not done this on their own. Therefore, the firings were illegal. And NSF was one of those agencies. Was in that group.

One other agency to visit for us is the Pentagon. This was a story by contributing correspondent Kai Kupferschmidt about cuts there to research that's social science. So Kai broke the story that DOD was ending funding for what's called the Minerva Research Initiative, or the MRI,

which was established in 2008. And at the time, the Pentagon billed it as social science for a safer world. The idea was that the Pentagon was going to give university researchers funding for unclassified research that would sort of help them understand the social science aspects of national security threats. And it's had its ups and downs over the years in terms of funding, but it's survived. But this time, it seems like it may have reached the end of the road. What kind of

studies were they doing? They kind of ran the gamut. Folks were looking at the impact of climate change on national security and armed conflicts. Other folks were looking at things like, does access to fish stocks, does that create conflict? And how would that fuel conflict in places like the Sahel? Very wide range of research. So these are all ongoing research projects or recent research projects, and everything has been canceled? Is that what we mean when we're saying Minerva's

not looking so good right now? Well, so what we've heard is from a number of researchers funded by Minerva that their projects have been terminated or that they're not going to get money that they thought they were going to get. Other researchers have said they haven't heard one way or the other yet. So things are a little bit up in the air.

So that's kind of a little whirlwind tour of what's happening with the agencies. But one of the biggest pieces of news this week is these tariffs that were placed on some of our biggest trading partners. Those went into effect overnight last night. What do we know about the effects those are going to have on science in the U.S.? Well, we don't know a lot yet. But yes, Trump has imposed new tariffs on products coming from China, products coming from Canada and products coming from Mexico.

What we do know is that China is the leading manufacturer of all kinds of things that are used in scientific laboratories and clinical settings. And Mexico and Canada are not that far behind.

Research labs depend on electronics, glassware, plastics, all kinds of things that are either made or assembled in those countries. And now, presumably, at least some of those products are going to be subject to these tariffs, which will raise costs. Yeah, overhead costs, if you will. Yes, overhead costs, if you will. So researchers may be looking at higher tabs for conducting their research.

Okay. Let's talk a little bit about the reaction in the scientific community. So science societies have written a letter this week. Can you talk about that? Yeah. So 48 societies who say they represent almost 100,000 scientists

wrote a letter to members of Congress basically asking them to protect research in the United States. They basically say what we're seeing under Trump is unprecedented in terms of the potential to undermine the research ecosystem as the United States has known it for 50 or 60 years.

And so they're asking lawmakers to really step in, use their power of the purse, use their influence to make sure that key programs are protected and that the basic infrastructure is protected. And the last thing I wanted to mention was the March coming up for scientists. This is something we've covered, I guess, out of the annual meeting a few weeks ago, but it's actually coming to fruition at the end of the week here. Yeah.

Yeah, so very similar to what happened under the first Trump administration, there's sort of been this grassroots upwelling in the scientific community of folks looking for a way to demonstrate broad public support for research and for science. Some younger researchers have gotten together and organized this stand up for science set of marches. There's going to be one here in Washington, D.C. They've also got marches planned. They're trying to do marches in state capitals.

around the country and presumably in other locations too if local organizers are able to pull it off.

So we'll see what it looks like. The March for Science, which occurred under the first Trump administration, was global in nature, and literally millions of people showed up all around the world. I don't know. We don't know what the turnout for these events will be, but it will be very interesting to watch. Yeah. Thank you so much, David. David Malikoff is the international news editor for Science, and he is helping in a big way manage our coverage of this administration.

You can find all of our science policy coverage at science.org slash science insider. Stay tuned for a story on researchers using genealogy and DNA testing to find surprise people in the family tree.

Hi, Science Podcast listeners. This is Kevin MacLean. I'm one of the producers on the show. I just wanted to hop in here before we get started to ask you to consider subscribing to News from Science. Every week on the podcast, we bring you one of the stories that the News from Science team has published, but there's so much more than what we can cover on our show here.

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He had a great uncle and I was fascinated by his genealogy. He knew everything about all the generations. But a sudden moment, he stopped with it, with genealogy. And that's because he heard in the news that 10% of the fathers are not... 10%? Yeah, 10%. That was absolutely...

the figure in the 90s and beginning of the 2000s, that 10% of the children has another father as assumed. And he was just 10 generations back in time in his paternal line. And he quitted with his hobby because he said, that's not my ancestors anymore. I was only 10 years old, but I always remembered that. That's your origin story. That's my origin story. This is Martin Larmazzo. He's a genetic genealogist who studies extra-pair paternity.

Martin compares meticulously produced genealogies that trace back through the last name of a family and compares that with how the Y chromosome is inherited.

Just like a last name in some societies is always past father to son, the Y chromosome always goes from father to son. There's no mixing of this chromosome. It's a lot easier to trace over many, many generations. And so if you have a really good genealogy, you can look at people who are alive today that are very distantly related to each other, and they should have the same Y chromosome, unless somewhere along the line, one of the fathers is not the

the genetic father. There's an extra pair paternity event. Contributing news correspondent Andrew Curry wrote about this idea for a feature this week. I met Martin at an ancient DNA conference, actually. He gave a presentation on his research, and I was just totally fascinated by this combination of genetics and genealogy.

In addition to doing the DNA analysis and figuring out this method, he had to go out there and convince people to give him DNA samples. For us, a research question that's sort of personal and you could see how people would be reluctant. Yeah. If it weren't a private, sensitive thing, we would just survey people and ask them, right? Exactly.

Exactly. Yeah. I mean, he said you can't reliably get information on this by just interviewing people on the street. And obviously, it's hard to find out about the past, too. Extra pair paternity is very bespoke, right, to this genetic genealogy field. Is this the first time you've encountered it, like working, talking to Martin?

I think so. And I think it's a term that he prefers to cuckoldry, which has a strong implication that it's an intentional deception on the part of the woman. Whereas extra pair paternity leaves open a lot of different possibilities. The important part of it is that it's different than what's in the legal genealogy. There's this mismatch between the genealogical record and what the genetics is telling you.

but we don't know if it's, for example, a result of rape or it could be cuckoldry or something else. This is a sensitive topic. Even if, like Martin, you stay well in the past. He worked, for example, with a group of people that all have the same last name

as the famous composer Ludwig von Beethoven. Apparently Beethoven had a number of health issues in addition to his deafness, like stomach issues, he had alcohol problems. He actually signed a letter or wrote a letter at the end of his life saying, "If my doctors can figure out after my death what I suffered from, that's of interest to me."

Much, much later, researchers took that as sort of a consent form. There was this genetics project to look at whether they could figure out from his DNA what his health problems were based on hair samples. So they had hair samples that people claimed had been collected from Beethoven at some point during his life.

you know, in collections all over the world. And they wanted to compare the DNA from those hair samples to living relatives to make sure they were actually related to Beethoven. The first approach was to call in the people they thought were his relatives. Made the whole genealogy of that family. And I find still 154 people living today worldwide. And they are almost all in Flanders or in Belgium. We went to Bonn where Beethoven was born.

We went there and there were really the heroes of the day and going to the mayor and on the television. But I also sampled several persons.

for the Y chromosome because they are all connected with Ludwig van Beethoven. Like my extra-perp paternity studies, I never study brothers or nephews because, yeah, that's not ethical and they also want to celebrate Christmas in the future. So you pick people that are pretty far away from each other

in the bottom of the tree, you know, in modern times. You don't want cousins or brothers because then you might have to reveal to them that living people that they think are their relatives are not actually biologically related to them.

It's not something you want to do that's not very ethical when really you're just looking for information about Beethoven. I select people who are very far related from each other based on the genealogy. All the five males that we selected, they all had the same Y chromosome, except for Ludwig van Beethoven, who had a completely other Y chromosome.

And so somewhere in the last 17 generations of Ludwig van Beethoven, there should be an extra paternity because there is nothing wrong with the legal genealogy. I spent one year in the archives to be 100, 100% sure. So you said, okay, I'm following all these birth records, all these marriage records. Oh, and also testaments, all us testaments and records. And you find this.

Big wide swath of relatives, according to the documentation. And then you tested along that layer and none of them are related to Beethoven? No, no, no.

There's more to this than gossip or, you know, maybe being related to Beethoven. In fact, for a lot of musicians and music historians, it's really important to know the emotions of Beethoven, how he perceived also family. You can only understand that person, Ludwig, and his music if you understand also his emotional world.

And seeing that his father had not a good connection with his grandfather, the grandmother went to a convent because she had an alcoholism problem and apparently maybe also has adultery or rape issue. But she had to leave Bonn.

Back in modern times, Beethoven's supposed descendants were really, really not happy. It was really a big thing because their whole life is about, yeah, I have the same surname. And if someone meets them, every time they say from Beethoven, are you family? And it was always yes, yes, yes. And now you have to say it's complicated. It really is.

change their identity. And it was very difficult, even if it was hundreds and several generations between each other. It still means a lot for those people. The Beethoven study is a very specific example of extra-pair paternity, but Martin has taken a look at a very diverse group of genealogies from this part of Europe.

The aim is to get a handle on how frequently extra-pair paternity is happening in this historical time, so going back a couple hundred years. How often does this really happen compared to that 10% number that upset Martin's great-uncle at the beginning of the story? Martin did come up with a number, and he shored it up by looking past the Y chromosome to mitochondrial DNA. Y chromosomes are useful because they're passed down generation to generation with little change.

What about the female lineage, though? Just like men pass the Y chromosome down to male offspring, women pass mitochondrial DNA to their offspring. Martin also did a study based on the mitochondrial DNA. When he started it, people were sort of shocked because genealogy is so wrapped up in following your patronym, your father's name back in time. People didn't even realize you could do it for women.

they do change their names and they do leave their homes often more often than the men. Yeah. And in Europe in particular, it takes a lot more work, but it is possible. In that point, you're trying to figure out again, is there a discrepancy between what's written down about this lineage of women and then what the genetic relatedness? Yeah, exactly. If the mitochondria matches, then the genealogy should be the same. And it was sort of a proof of concept because

because it should be much rarer for women to not be the mothers of their children, their legal children, because women always know. But he did go back and look and none of the mismatches stood up to scrutiny. They were usually mistakes that people had made in the historical research.

When you look back through successive generations of a Y chromosome, you do see these mismatches where the father's Y is not being inherited. When you go back through the maternal mitochondrial DNA, if there's a mismatch, if it's not what you expect it to be, it's because of an error in the paperwork, not because people were trying to hide it.

who the mother was? Correct. People had said, well, you know, what if there were a lot of secret adoptions in the past? And it's not kukuljri, it's something else. And he said, well, you know, then let's look at the female line. Right. And if there are a lot of secret adoptions, then we'll see. And there weren't. And one of the things that

was kind of the goal of this research was to put a number on this and say, oh, this is how common it was because there was this zombie statistic running around saying 10% of offspring. We don't know who the dad is. Right. And that zombie statistic kind of dates back to the 70s. And it was based apparently on early studies from paternity tests. But if you go in for a paternity test to begin with,

you're expecting something to be wrong. So that's a biased sample. It sort of took hold and it was repeated in journalism. But then the number that Martin has come up with is one-tenth of that? Yeah, I mean, it's an order of magnitude lower. Right. It's like one, one and a half percent for the European samples that he's done. That's right. And there have been a few samples from elsewhere in the world that have backed that up, at least in sort of patriarchal societies. Because there are places where

parents are not necessarily biologically related to their children. And it's the norm socially, right? Yeah. And there are places that are very non-European where the social structures are completely different. Even in modern society, adoption, fostering, stepchildren. Absolutely. There are lots of cases where you feel just as strongly that somebody is your child and you know there's no blood connection. Being a social parent as opposed to a biological parent is very common today.

And it has kind of risen and fallen in history in different places. Different societies take different approaches to it. This research is able to look, you know, in the last 500 years. And then more recently, ethnographers have gone to societies where paternity looks very different.

Brooke Seltzer at UCLA worked with this community in Africa called the Himba, where people who are not biological fathers are usually totally aware. So I began working in northern Namibia with a group of rural pastoralists back in 2010. And I had originally gone there to study materialism.

maternal and child health, mother-child issues. And I began that work by doing reproductive histories with women. And pretty early into the interviews, the women started telling me about the children being fathered by someone other than the husband. And so these were children born into marriage, so it wasn't out of wedlock births. And they were very forthcoming about it. So that

intrigued me. It seemed to go against a lot of what I had learned as an evolutionary scientist about how people think about extra pair relationships. The way that I had learned about this was that those would be pretty restricted. So Brooke and her colleagues decided to do a more quantitative study about extra pair paternity using genetic testing. This might actually be a pretty sensitive investigation to do in a small community.

I think it's more possible here because people both were forthcoming and willing to talk about it. The norms for women who had extramarital partnerships were different so that women were unlikely to be sort of persecuted for having an extramarital partnership. So that made it a safer study to do. And the third thing is that...

they already had these strong conceptions about biological versus social fatherhood. So it wasn't something that we had to explain to them that the

the genetic test would bring out. They were going to be shocked by a mismatch. We were that maybe people still might be upset at an individual level because people are people, right? And even though people said it doesn't really matter, I said, well, could you think of one person in the community who might be upset if they found out they were the father when they didn't think they were or they weren't the father when they thought they were? And people said, yeah, I wouldn't be upset, but I could imagine that somebody else might be.

So because of that, we wanted to put all of these protections into place, even in a place where people were pretty open about all of this. They collected genetic data and they collected reports from men and women about who they thought the biological versus social father was of the children in the community. But they didn't release specific information to specific people. Instead, they looked at averages over the whole group.

One main question was just whether the extra pair paternity rates were going to map onto the high level of extramarital partnerships that we were seeing. So did this actually have consequences in who was fathering children or were these extra pair partnerships so sporadic that they were unlikely to result in pregnancy? What we found was that it mapped on quite well. So it was 48% of the children born into marriages were fathered by someone other than the husband.

How did that line up with the reported parentage from the people in the community? Turned out that both men and women were about 70 to 75 percent accurate. And when we presented that data to them, they said, oh, no, no, we're better than that. And I said, well, what do you mean? And they said, well, there are going to be times when we will tell you that we are the father of that child, even when we strongly suspect that we're not.

The reason that they were doing that was because they have these really strong ideas about social fatherhood.

So we were actually able to look into that because we knew which direction they were, quote unquote, wrong in. Were they wrong where they said they were the father and they weren't? Or were they wrong where they said they weren't the father and they were? And 90% of the time that they were wrong, they were wrong in the direction that they had told me they thought was the case, which is that they said they were the father when they weren't. I'm going to go over those numbers one more time. About half the children had extra pair paternity.

And when the adults were asked whose child was whose, they were right about 70 percent of the time. But then when pressed a little further, they were even more accurate. So that was a really, I think, a really good lesson in why you should continue this community engagement all the way through the process, because it it will turn up something that maybe I wouldn't have thought to look at.

That's super fascinating. How good are people in other societies at guessing paternity like this? So one of the best kind of meta-analyses that's been done of paternity data comes mostly from Western samples. This was work done by Kermit Anderson. If you look at paternity clinic data, those are cases where men are going in because they suspect that they're not the father. About 30% of the time, the men are

were not actually the fathers. And if you kind of flip your thinking about that, what that means is that those men who suspected that they were not the

the father, were wrong about 70% of the time. And with HEMBA, they were, what, about 70, 75% accurate. So almost exactly the opposite of what we found in our results. Okay, this is paternity clinics. The rate estimated from studies that don't have anything to do with paternity, for example, uncovering extra pair of paternity in a genetic study that doesn't have anything to do with it, researchers see the number one, one and a half percent

extra-pair paternity, at least in these U.S. Western studies. The numbers you're talking about with the HEMBA are 50%. Are we just seeing, you know, a range of human behaviors here or is something else? Is there anything else we can say about this? I think we are just seeing a range. They probably are at the high end of the range. But yeah, I mean, the 1% numbers make perfect sense to me. They map onto the cultural norms in the places where those data come from, right? Just like the 48%, I think,

That's pretty well onto HMBA norms. So I think we should expect this variation. I think that's one of the lessons actually, is that when you only get data from

places like the U.S. and the U.K. and Europe, and you see that 1% over and over and over again, you start to think, oh, well, is this a human universal? That's part of the error of only collecting data from really similar types of societies, right? It's really important to go specifically to the places where you suspect there might be more variation and look at these questions in those places.

If you did just kind of helicopter in and take genetic samples in a bunch of places, you wouldn't know why you were getting the different rates that you were getting. Yeah. I asked Brooke if the Himba people are jealous of each other because this is a problem in other societies. You know, we're talking about Kukuldri a lot when we're talking about the Western extra pair paternity.

And she says, of course, the Himba feel jealous, but they're just not as willing to express it. Well, a lot of the folks I spoke with agree on is kukuljri, this idea that men are being deceived is definitely a Western cultural obsession.

It's important in other societies as well. And for women, if there's a huge risk to having a baby with somebody who's not your partner, social risk, physical risk, then you're less likely to do it. So these social and religious norms are

aren't irrelevant, and they also push the rate down in Western societies. When we talk about the modern day, there's single parenthood, adoption, stepchildren, people not being married and having kids.

Is that something we can really compare with, you know, looking at marriage records from Germany that go back three, five hundred years? Can you compare that with someone getting genetic testing today and finding out they're not the biological father of a child they thought they were? Martin just published a paper on...

how shocking it is for people to find out from these direct-to-consumer DNA tests who's not related. And there was another paper that came out recently about how doctors are trained to talk to people about their parentage. And it is a shock to people. And the direct-to-consumer DNA industry doesn't provide counseling or any particular warnings or support. And I think that's something that Martin is trying to change. It is relatively rare, but

but in absolute numbers, it is still a lot of people. And you should be careful when you notify them because it has psychological consequences.

Andrew, where is all of this going? Where is this tending to? We're talking about genealogies going back in historical time, a couple hundred years. We're talking about rates of extra-pair paternity in different societies in modern day. Where else can you see genetic genealogy playing a part? I think for me the most exciting, as somebody who covers archaeology, is that people are using DNA to look into ancient kinship and genealogy.

ancient DNA is being used to get into more and more historical period questions. There have even been studies recently where they've taken ancient DNA and compared it to people in the 23andMe database and found modern relatives.

So as genetic genealogy develops and ancient DNA starts to answer more historical questions, like the Beethoven study, I think there will be some really interesting things coming out. I think the extra pair paternity, you know, probably won't play a huge role in

But I think the questions that it can answer and the way that you can connect historical records, genealogies, documentation like that with DNA has a lot of promise to be super exciting. Thanks, Andrew. Thank you. Yeah, it was great to be here. Andrew Curry is a contributing correspondent for the news team. You can find a link to the story we discussed at science.org slash podcast.

Up next, the role of stress and hormones in intrusive thoughts. This week, Science Advances is publishing a collection of articles on research into women's health. The package includes papers on a variety of topics, including the complex interplay between menopause and Alzheimer's risk, and how aging in women activates unique mechanisms in the brain. It also covers new takes on

on the science of reproductive health and explore psychological, systemic, and policy issues. On the podcast, we have Suzanne Schweitzer to talk about her article on intrusive thoughts and peripartum anxiety. Hi, welcome to the podcast. Thanks for having me. Sure. Your article is part of this collection that highlights advances in women's health, which is a long, under-examined area in science. Is this peripartum intrusions that we're going to be talking about?

also understudied? Absolutely. The first I came across it was when I experienced them myself after giving birth to each of my three kids. I wasn't prepared for them. I didn't know about them. I'm a trained psychologist. I had 10 plus years of training under my belt by that stage. And I had never read or heard about them, nor had I been told about them in any of my antenatal care. And I had

three kids in three different health care systems as it's coming in academics. Yeah. So let's talk a little bit about what they are. So I mentioned this to my sister-in-law this morning. I'm going to do an interview on this and I'm so interested because I had it and she had it. She said yes. On the way home from the very first doctor's visit with my infant, he was less than two weeks old.

We're in the car. We're on the way back home. I want to get coffee. I tell my husband and I said, I want to go to Wawa, get some coffee. And he was like, well, I have to go to Royal Farms, this other place. Why don't we just get coffee there? And she said, I thought to myself, I'm going to throw myself out of this car. Just get out because that's where the Wawa is. She didn't do it. But it was this like thought that she would never have expected. And she said, I had so many weird thoughts the entire time I was kind of going through

the postpartum period. And I had the same, not that same one, but definitely. Absolutely. They are incredibly common. In fact, we think nearly all women have intrusive thoughts in the perinatal period, especially in the postpartum period. We know that virtually all women have thoughts of accidental harm coming to the child. So that could be a thought like seeing them fall off the changing table in your mind.

or seeing the pram roll away. Those kinds of thoughts are really, really common. But then about half of all women also have intrusive thoughts of intentionally harming their child. And as you can imagine, that's incredibly distressing. It's really, as a human, the most awful thing you can think of, harming any child, let alone your own. And as your sister describes, they come out of nowhere, these thoughts. They are not

thoughts you've previously had. They're not thoughts that are familiar. They're not thoughts that you expect. And that's what makes them so highly distressing. It's alien to you. It's totally alien. So in psychology, we refer to this as ego dystonic. So they're in complete contrast with your entire belief system, with your entire value system. You dearly, dearly love this child and you most certainly don't want to harm them. But you all of a sudden have these thoughts and, and

We don't know very much as to why these thoughts are happening yet. As we discuss in this article, we think there's a number of vulnerability factors that place women at risk for finding these thoughts, particularly distressing. During pregnancy and postpartum, do they tend to be on a theme of worrying about your kids' health or being concerned about them? Or is it kind of all over the map? So these are specific thoughts.

of infant-related harm. So while you can have, in pregnancy, there have also been thoughts noted, in particular around birth, so intrusions around, you know, what the birthing process will be like. There are some intrusive thoughts that have been noted in the pregnancy period around the relationship. So the partner suddenly being absent, the partner being unavailable at the time of birth and things like that. But it is in particular, both during pregnancy and

especially postpartum, around harm coming to the child. There are some explanations that people have come up with, but they're not exactly easy to scientifically ground truth, right? Because it's like,

This helps you be more aware of dangers if you think about all the dangerous things that could happen. But it's not necessarily helping for a lot of women. It can be very stressful. We think that this awareness of threat in the caregiving environment is probably what made them occur in the first instance, why they're evolutionarily speaking adaptive thoughts. You will become extremely vigilant, resilient.

when you have these types of thoughts of any danger coming to your child. However, we don't know yet why, which is clearly a normative experience if virtually all women have them, why they are associated with poorer mental health in both the mother and we've also seen in the child

So if they're normative, why do those who have them more frequently, then are they more likely to experience mental health problems? And that's what a very small body of research at the moment, but which we're hoping to build, is looking into. And that is looking at different cognitive as well as biological vulnerability factors. Are there certain stressors or factors that make it

Maybe it's still normal, but it is more harmful for the person experiencing them. So we know factors that make these types of thoughts more maladaptive in other conditions, in other periods of life. For example, if we draw on the trauma literature and also the OCD literature, we know that how we appraise these thoughts is critical in their impact on our mental health trajectory afterwards.

So if I can accept this thought as simply an intrusive thought over which I have no control, that just randomly, clearly in my primary brain has some utility in protecting my infant and comes up, and then I can let go of that. That is one thing. But if

If I appraise this thought as I am a bad mother, I'm having this thought because I don't, I cannot possibly truly love my child if I have a thought like that. Or if I think things along the line that this must mean that I'm going crazy, this is not normal. Those type of what we call maladaptive appraisals will make these thoughts more distressing and

And especially if I experience a thing that is common in OCD, which we refer to as thought-action fusion, those people who have strong thought-action fusion think that because they're having a thought, it means they will act on it. And so if I have a tendency towards strong thought-action fusion, I will be, again, more at risk from these thoughts of thinking that I could possibly harm my child.

And then a third cognitive factor, which again, we know from other literature amplifies the impact of intrusions and intrusive thoughts is repetitive negative thinking. So these are things like worrying and rumination. And again, you can probably well imagine how if I can just let that thought go, then that's one thing. But if I then think over and over about this, you know, initially thought, but it almost takes on memory-like properties because it's so aversive and it

creates so much distress. So that can be really maladaptive. And we think that that may be cognitive mechanisms through which these thoughts are associated with poorer mental health outcomes. Mental

Mental health problems, as you write in your paper, are more common during postpartum, during pregnancy. People can get anxiety, depression, and at the extreme end, there's postpartum psychosis, which is extremely, extremely rare. But can you talk a little bit about how postpartum psychosis is different from having intrusive thoughts? That's completely qualitatively different.

You know, we were talking a minute ago about these thoughts being ego dystonic, so in complete contrast with your belief system. And when you're in a psychotic episode, that no longer applies because your reality, your belief system has switched. You're in a different type of reality. So those thoughts are not necessarily, you know, in contrast with your beliefs anymore. They can very well fit within this psychotic episode.

Yeah. So intrusive thoughts, they're not signs of the side of psychosis, but they can be very distressing. And one thing I thought was so interesting, and you kind of already alluded to this, is that intrusive thoughts, memories, images are known to be part of different mental illnesses, but they're not very predictable. It's not easy to get a handle on when they're going to occur. So looking to people who are pregnant or postpartum is a way of kind of like narrowing it

in and saying, let's take a really close look at this special case and see if it generalizes. That's such an important point. So as you say, they're unpredictable typically. So that makes them really hard to study. But the postpartum period offers this unique opportunity because as we were saying earlier, virtually 100% of women, nearly all women experience these type of intrusive thoughts after they've given birth. And so all of a sudden that allows us to start and study and

antecedents and factors that lead to these intrusive thoughts and that are involved in their maintenance. So of course, given that is happening in this perinatal period, then an obvious thing to look into are hormonal contributions as well. The magnitude of shifts in hormones and changes in hormones is greater during the perinatal period than your entire hormonal changes across your lifespan combined.

it's been studied in the context of postpartum depression. In the context of postpartum depression, what's been observed is actually not the magnitude of that change that differentiates women who are susceptible to experiencing postpartum depression compared to those who aren't. But instead, it's the sensitivity to hormonal changes that appears to be related. That said,

We know incredibly little about hormonal sensitivity. In general, we've got a bit of a better handle on it across the menstrual cycle. But in the context of the perinatal period, we actually know very, very little about how differential sensitivity to these hormone changes may be putting women at risk and again, making them more susceptible for mental health problems, but maybe also this phenomenon of experiencing intrusive thoughts. So the

The idea then would be to look at how a woman responds to hormonal shifts during, say, her menstrual cycle, and then say, we see something in here that suggests that pregnancy is going to have a stronger effect on this person. Is that what the idea? I absolutely suspect that that is what's going to be indicative, but that's not that at the moment. We're not there yet. No, we're not there yet. But I actually think that this is going to be highly predictive of...

of susceptibility to perinatal mental health problems in general. If we look at literatures such as, again, the trauma literature, we can see that intrusive memories and the experience of intrusive memories has actually been associated with changes in female sex hormones. We also know that shifts in hormonal sensitivity are associated with changes

changes in ruminative, so repetitive negative thinking, but also changes in the way in which we process fear and threat. So together, that starts to draw a picture of maybe those hormonal changes, and in particular, the sensitivity to those are what may make women more prone to experiencing intrusive thoughts in the perinatal period. And in turn, those who then have those cognitive vulnerability factors or heightened hormone sensitivity on top of that, may be then the ones

for whom these thoughts become really distressing and puts them at risk for developing perinatal anxiety or indeed other disorders such as OCD and depression. What does hormone sensitivity look like? You know, how would that be detected? As women, most of us will have experienced fluctuations in our mood across the cycle. And for some, these can be barely noticeable changes, if noticeable at all. But for

But for others of us, there can be really drastic changes in our mood leading up to a menstrual cycle. And for some of us, it becomes so debilitating that indeed we're diagnosed with what's called premenstrual dysphoric syndrome. So we actually experience something akin to a depressive episode every time in the lead up to pregnancy.

our menstrual cycle. And obviously that can be really debilitating, but that sensitivity, that sensitivity due to shifts in hormone is what we refer to as hormonal sensitivity. Okay. So it's not that they're getting bigger doses or bigger changes. It's just the way they react to it is going to be on a scale. It's going to be more sensitive or less sensitive. That's exactly right. The coupling of the mood and

and hormone change level, irrespective of the magnitude of set change, is tighter. Do we know anything about what is linking those things? How they connect? We don't yet. There is some work in the premenstrual space starting to draw these things apart. I was...

quite interested in finding out about people's experiences more than the scientific side of things. When I was pregnant, it just was what my focus was on. You hear a lot about what you should worry about. You get this like litany, like, oh, make sure there's no hairs around your baby's toes. Make sure no fingers get pinched and buckles. There's all these like very specific threats that are just listed out there for anyone who's anxious to go

keep track of. But to think that it's kind of creating this arsenal of intrusive thoughts, it's just kind of interesting to try to balance those two things because you think you're preparing yourself for dealing with a baby. And in fact, you're also creating your own nightmare. Absolutely. And it's just really fascinating how under-researched it is. Part of the piece is, as I'm sure is made abundantly clear with this issue, it's a women's health issue. They're

therefore, by definition, considered niche. It isn't. It applies to half the population. And by the age of 44, 85% of us will have given birth. So it really, it isn't niche. And it applies to virtually all of us who give birth. So I think it's incredibly important to study, but also to create awareness around it. Because what makes it really, really tricky is, of course, women are reluctant to disclose those thoughts, especially women.

those of us who experience thoughts of intentionally harming our child, because rightfully, in some cases, we worry about that raising child protection alarm bells with practitioners. So it's really, really important to start to educate women, but also healthcare practitioners around the prevalence of those thoughts and how they're different from thoughts that are associated with actual threat to the child. Because

Again, in a number of studies now, people have shown they are not associated with actual harm coming to the child. Thank you, Suzanne. I really appreciate you coming on the show. Thank you so much. It was a pleasure. Suzanne Schweitzer is a Scientia Associate Professor at the University of New South Wales. You can find a link to the Women's Health Package and Science Advances at science.org slash podcast.

And that concludes this edition of the Science Podcast. If you have any comments or suggestions, write to us at [email protected]. To find us on podcast apps, search for Science Magazine or listen on our website, science.org/podcast. This show was edited by me, Sarah Crespi, and Kevin MacLean. We had production help from Megan Tuck at Podigy. Our music is by Jeffrey Cook and Wenkoy Wen. On behalf of Science and its publisher, AAAS,

Thanks for joining us.

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