Science Friday - Nasal Rinsing Safely | How Your Brain Constructs Your Mental Health

Episode Date: March 15, 2024

A recent study looked into life-threatening Acanthamoeba infections, and a few deaths, linked to the use of tap water with devices like neti pots. And, in ‘The Balanced Brain,’ Dr. Camilla Nord explores the neuroscience behind mental health, and how our brains deal with life’s challenges.Scientists Warn Against Nasal Rinsing With Unboiled Tap WaterResearchers at the Centers For Disease Control and Prevention published a study Wednesday that examined 10 cases of life-threatening Acanthamoeba infections that occurred after people cleaned their sinuses with neti pots, squeeze bottles, or other nasal rinsing devices. In most of these cases, which occurred in immunocompromised individuals over the span of a few decades, individuals had used tap water for nasal rinsing.Tap water, while generally safe to drink, is not sterile. Microorganisms and germs live in distribution systems and pipes that the water travels through, and Acanthamoeba amebae was the main link between the 10 cases, three of which resulted in death.Although contracting the Acanthamoeba pathogen is extremely rare, many people are unaware of the unsterile nature of tap water and use it for their sinuses, according to a survey study published last year. A third of participants incorrectly believed U.S. tap water is sterile, and almost two-thirds assumed it was safe to rinse your sinuses with it.The CDC and FDA recommend using distilled or sterile water for nasal rinsing. If you want to use tap water, they recommend boiling it for three to five minutes and allowing it to cool. While slightly more time consuming, it is an effective way to get sterile water.Rachel Feltman, host of “The Weirdest Thing I Learned This Week,” joins Ira to talk about this story and other news in science this week, including a new study that links microplastics in the human body to increased risk of heart disease and death, why the U.S. maternal mortality rate might be inflated, and why cicadas produce high-speed jets of urine.How Your Brain Constructs Your Mental HealthIf you’ve ever struggled with a mental health issue like anxiety or depression, or know someone who has, it’s pretty clear that what works for one person might not work for another. Antidepressants only work in about 50-60% of patients. Meditation or yoga may be a gamechanger for some people, but ineffective for others.Over the past few decades, neuroscientists have made huge advances in our understanding of the human brain. How can we use the latest neuroscience research to help improve our mental well-being? And what is the relationship between physical and mental health?To answer those questions and more, SciFri producer Shoshannah Buxbaum talks with Dr. Camilla Nord, director of the Mental Health Neuroscience Lab at the University of Cambridge and author of the new book The Balanced Brain: The Science of Mental Health.Read an excerpt of The Balanced Brain at sciencefriday.com.Transcripts for each segment will be available after the show airs on sciencefriday.com.  Subscribe to this podcast. Plus, to stay updated on all things science, sign up for Science Friday's newsletters.

What can being hangary, you know, that feeling of being angry because you're a little hungry, teach us about the relationship between our physical and mental health. The way that our brain codes for internal bodily states like hunger is very much overlapping anatomically with the way that it codes for emotions. It's Friday, March 15th, and today is Science Friday. We made it. Congrats. I'm SciFri producer Shoshana Bucksbaum.

A little later, I'll talk with a neuroscientist about the biology of mental health, how mental and physical health are related, and ways to improve mental health treatments using the latest neuroscience. But first, Ira Flato talks with science journalist Rachel Feltman about some alarming new research into the microplastics found in our bodies, plus other top science news of the week. In space news, reports of the death of Voyager 1 may be premature. NASA sent a signal to the faraway probe and was able to decipher meaningful information from it, keeping our fingers crossed as NASA wizards figure this one out and hoping this is nothing more than the aging spacecraft forgetting where it left the car keys. There is concerning news this week, though, about microplastics being found in our bodies and now in our arteries. Last week, scientists in the New England Journal of Medicine published a study that linked microplastic presence in arteries to higher risk of heart disease. Ooh, here to explain that study and other science news from the week. It's Rachel Feldman, host of the podcast, The Weirdest Thing I Learned this week,

Rachel is based in Jersey City, New Jersey. Hi, welcome back, Rachel. Hi, thanks for having me, Ira. Let's go right to this microplastic study. It sounds alarming. Yeah, you know, it is alarming. We've been seeing for years now that microplastics are everywhere. You know, they're in freshly fallen Antarctic snow.

They're in the Mariana Trench. They're in the clouds above Mount Fuji. And they're in human blood, breast milk, lungs, and even placentas. But we know very little about how exactly they affect us. And that's where this new study comes in. They found microplastics within the plaque that clogs human arteries. and they linked its presence to heart disease and death. So, you know, we're getting closer now to actually understanding what these really insidious particles do.

Basically, researchers, they followed 257 patients who had fatty plaques removed from their carotid arteries. This was in 2019 and 2020. And of those 257, 150 patients were found to have polyethylene. inside their plaques, which is just really, really viscerally upsetting to me, and I'm sure many other folks. The study says that electron microscopy showed visible, jagged, plastic particles. But what's really troubling is that in following the patients for about three years, the researchers found that the people with those microplastics in their plaque were nearly five times more likely to suffer heart attacks, have strokes or die.

Oh, my goodness. Yeah. And of course, you know, they are quick to say this is a correlation. You know, they didn't show the exact mechanism. But you have to assume microplastics can't help when you have plaque in your arteries. And the thought is that it could be driving increased inflammation, which, of course, we know is bad for you for many reasons. So, yeah, I hope that we see a lot more research like this, even though I dread seeing it. Yeah.

Yeah. Well, speaking something to dread seeing is another story in a new CDC study on netty pots and tap water. Tell me about that. Yeah, always bringing you good news, Ira. So more than a decade ago, health officials in the U.S. linked deaths from brain-eating amoebas to the use of sinus irrigation tools like netty pots. But a new study from the CDC looked at 10 deaths over the last three decades from another. amoeba that they now say was likely also transmitted via sinus rinse. So this was a thing we

already knew could happen, but it's a good reminder because while these infections are rare, what's really worrying is that a lot of people don't seem to realize that they're putting themselves at risk. By using their tap water. Yes, exactly. So a recent survey found that a third of people believe that U.S. tap water is sterile, which is not true. It is treated to get rid of lots of microbes, but there's lots of stuff living in pipes. You know, there's lots of biofilms in our plumbing. So definitely not sterile. And 62% of people in that survey thought it was safe to use tap water for rinsing your sinuses. 50% thought it was okay for rinsing contact lenses. While tapwater is generally safe to drink unless something has gone wrong, lots of those microorganisms

that are in there that are safe to ingest are not safe to come into contact with your eyes. your sinuses or your lungs. So if you're using a CPAP machine, if you're using a sinus rinser, if you have contacts, you should always be using distilled water or boiling tap water for at least a minute, three minutes if you're at high elevation, and then of course letting it cool. So it's rare, but you really don't want to be in that small percentage of people who get a brain eating amoeba. No, I hate when that happens. And speaking of the CDC, they also have new travel guidance. right about the measles vaccine? Yeah, measles cases are going up in 17 states. And so now the CDC says if you are traveling abroad, you should go see your doctor at least six weeks before

to make sure that you are up to date on your vaccines because we are seeing cases of people who are eligible to be vaccinated, but who are not going abroad, getting measles and bringing it back and that leading to outbreaks in the U.S. There's a 30-fold increase in measles cases in Europe. And, you know, the solution is really simple. Get vaccinated. Make sure you're up to date. If you're at least six months old, you should be vaccinated against measles.

Hmm. Let's turn to some welcome news about death. If that's possible, it turns out the maternal mortality rate may not be as high as the CDC reports. Yeah, this is really interesting. because it turns out, while there's still reason to be concerned about maternal mortality in the U.S., a clerical error may have been skewing data. So the most recent reports from the CDC said that there was 32.9 deaths per 100,000 births in the U.S., which was really a shocking outlier.

For example, in 2020, the maternal mortality rate of all high-income countries was at 12 deaths per 100,000. So we were looking at close to three times as many in the U.S. It turns out that the real number may be closer to what you would expect, something around 10.4 deaths per 100,000. Researchers decided to look into this pregnancy checkbox that's on the National Death Certificate. It was added about 20 years ago. And it's apparently been known for some time that this leads to some clerical errors where really any time the box is checked, something tends to get registered as maternal mortality, even when the pregnancy had nothing. to do with the death. And in fact, sometimes people who weren't pregnant at all, this box gets checked accidentally. So researchers just dug into the data to try to pull out those sort of false positives. And they ended up with a number much closer to what we would expect. But the really important thing to note here is that even with this clerical error fixed, the racial disparities we see in U.S. maternal mortality rates persist. Black pregnant patients are still three times more likely to

die than white patients and most of these deaths are preventable. So it's not that this isn't a problem, but we always want to have, you know, the correct data when we're tackling something like that. That's right. Let me follow up that story with another one, which for some reason on this show, we're always coming up with a story about bodily functions, if you know what I mean, right? I know you do. Because this week comes news that cicadas have a bodily function that's more similar to larger animals than insects their own size. I know it's your stories. Tell us about it. Yeah. So luckily for all of us, there are scientists who study the fluid dynamics of pee. Thank goodness. And one thing that is generally true is that most large animals like us produce

like steady streams of urine while smaller creatures make droplets. As an aside, producing little P droplets doesn't mean that pee is like short range. Last year there was a study from these same researchers actually. I remember. Yeah, the glassy wing sharpshooter. It uses this phenomenon called super propulsion to launch its little urine beads off its butt at ballistic speeds. But anyway, these same researchers have now turned to cicadas, which I guess just like have to be the most aesthetically unpleasant insects in the world because they apparently break the mold and they produce urine in high-speed jets, the strongest stream of pee relative to their body size of any animal ever studied. So good for them. Wow. And this, I'm just my mind if you could see my brain.

And this is especially relevant now because we're expecting a double brood season this spring in the U.S. right? We are. We are having a dual emergence, a 13 and 17-year brood are overlapping in the same part of the country. The good news is that the overlap is very minimal. So while it's true that the country as a whole is going to see trillions of cicadas this year, most folks will see like a normal number for an emergency year. The broods are most likely to come into contact with each other around Springfield, Illinois. But even there, the overlap is likely to be like pretty incidental in like a few wooded areas. But, you know, if it seems like they're a little more obtrusive than usual, you can blame the double emergence. I don't think anyone's going to fact check that. Yeah, but now we know a

little bit more about them, so they're a little more interesting. Yeah, and maybe wear a hat when you're outside. All right. Last story, closer to home. It turns out that Mars's gravity might be influencing our oceans. Tell me about that. Yeah, it's so wild. Basically, researchers, they dug a bunch of sediment from the deep sea to try to track how ocean currents have changed deep sea ocean currents over the last 65 million years. And they found this cycle where currents were getting stronger or weaker every 2.4 million years. And they say the only way to explain that the interval is our planet's resonance with Mars or how our planet's gravity fields interfere with each other, which changes the eccentricity of their orbits. Basically, Mars,

pulls Earth slightly closer to the sun sometimes, which exposes us to more solar radiation, and that strengthens deep ocean currents. Wow. So it's not just climate change that's changing the ocean currents. Yes. And of course, the researchers were quick to say, you know, yes, we get exposed to more solar radiation when Mars pulls us closer to the sun. No, this cannot explain away climate change.

That is definitely still a thing that's happening because of. of greenhouse gases. But this is another phenomenon. And in fact, it might actually, they say, mean that ocean currents can, like, keep up some of their circulation once climate change has, like, deadened the water mixing that we rely on. I, you know, it's a small constellation, but, you know. Yeah.

Cue the Therriman Martian music. Wee. Coming. What? Thank you, Rachel. Always great stuff. Always good to hear from you. Thanks, Ira. Rachel Feltman, hosted the podcast, the weirdest thing I learned this week. Rachel's based in Jersey City, New Jersey.

If you've ever struggled with a mental health issue like anxiety or depression or know someone who has, it's pretty clear that what works for you might not work for others. Antidepressants only work in about 50 to 60 percent of patients. Meditation or yoga can help some, but be a waste of time for others. And yet, over the past few decades, we've seen huge advances in our understanding of the human brain. So how can we use the latest neuroscientific research to help improve mental well-being? To answer those questions and more, I spoke with Dr. Camilla Nord, director of the mental health neuroscience lab at the University of Cambridge, an author of the new book,

The Balanced Brain, the Science of Mental Health. She's based in Cambridge, England. Dr. Nord, welcome to Science Friday. I'm so excited to be on Science Friday. Okay, so I want to start out with the title of your book, The Balanced Brain. So what do you mean by a balanced brain? So in my book, I try to deconstruct the idea of what mental health means. I don't think mental health is about the absence of negative emotions and challenging experiences. Unfortunately, I think they're completely unavoidable in life. But I think that what mental health really is is your brain's ability to respond adaptively to those kinds of frequent challenges that we experience. And the way that it responds adaptively is through what I call the balanced brain. But these are actually many, many different processes happening in the brain,

integrating experiences that we've had, learning from them forming predictions about the future. Some of the experiences we have are from the outside world, as you might imagine, difficult, challenging things in the outside world, wonderful things we experience in the outside world. Some of them are from our inside world. It might be infections that we experience or other things communicated by our body. But together, these construct our brains model of our own mental health. and that's what I call the balanced brain. What I found interesting is that one of the key pillars of mental health that you point at is drive or motivation.

That's not something that I traditionally think of when I think of mental health. So what do you mean by that? What role does motivation play in mental health? So I want to speak about this both kind of conceptually but also biologically, because I think we all have an intuitive idea about what drive and motivation is. and that intuition is probably correct. So we need the motivation or drive to engage with the world in order to experience any of the many positive things

that we might be able to learn from and build mental models of the world about. And then on a more biological level, drive or motivation is often the thing disrupted that is most measurable across species. So if you look at animal models of depression or other kind of mental health condition like experiences in rodents, for example,

example, drive and motivation are some of the most measurable phenomena that we can see disrupted. I want to dig a little bit into that. So in the book, you start out talking about pleasure, and that's obviously important for your mental health to be able to experience pleasure, want to experience positive things in your life. How does pleasure show up in the brain and relate to motivation? So the reason I think pleasure is particularly interesting, in the brain is because it has this relatively unique neural architecture from person to person. So this is reflected in the fact that the things you like aren't necessarily the things I like. But in your brain, this is the specific hotspots of pleasure that are dotted around the brain,

regions that if stimulated with electricity can cause the experience of pleasure. They're small, they're distributed, and they're also somewhat unique person to person. So it's this kind of very fascinating mapping of your likes and also your dislikes at a biological level in your brain. And this is, I think, actually quite a distinct and measurably very independent system from the one involved in drive and motivation. So I'll give the example of a much beloved neurotransmitter, which is dopamine. And one of the sort of pet peeves, I suppose, I have about dopamine, isn't that it's not great. I love dopamine as much as the next individual. But what we like about dopamine as a society is not really what dopamine is doing in the brain.

Often what you hear people say, oh, you know, I do dopamine dressing, or I'm interested in a dopamine diet, or I'm interested in a dopamine detox, what they're really talking about is pleasure, which is not really something particularly coded by dopamine in the brain. It's much more involved in other neurotransmitter systems like opioids in the brain, endogenous opioids, which you might have heard referred to as endorphins. Dopamine is much more closely tied with motivation and drive, the desire to do anything at all. So I want to move on to a phenomenon that you write about being hangary, this combination of feeling angry and hungry simultaneously. I've definitely felt this before. Probably listeners at home have experienced this.

What does this help us understand about the connection between our physical and mental well-being? What's so cool about hangary isn't just that it happens. Of course, if you have different kinds of biological disruptions, you know, you're cold as well. It can affect your mood. If you're too hot, it can affect your mood. But actually sort of why it happens. So I'm also a prolonged sufferer of feeling angry. It has a really, really big impact on my life. And different people are and aren't to different degrees, which is actually quite interesting. But the thing that it tells you about the brain is that the way that our brain codes for internal bodily states, like hunger is very much overlapping anatomically with the way that it codes for emotions like anger.

And in fact, many would argue that the way that we've sort of learned to identify what an emotional signal is is by reading signals in our body. So, for example, if you are saying to yourself, oh, I think I feel a bit stressed or anxious right now, what you're doing, one of the things that you're doing is reading signals from your body. You might be reading your own heartbeat or you're breathing, and your brain is interpreting that and making a prediction about why you're feeling that way. And sometimes those predictions are wrong, are misinterpretations. Treatments that we have for a lot of common mental health disorders don't always work for everyone. There's often a lot of trial and error. And, you know, for example,

the gold standard treatment for depression and anxiety is a combination of both medication, usually antidepressants and psychotherapy. But you suggest that patients might benefit from taking some type of medication actually before a therapy session. So how might that work? What is that tapping into? So at the moment, we treat patients relatively separately in terms of the treatments we think of as biological, like giving someone antidepressant drug, and the treatments we think of as psychological, like cognitive behavioral therapy. But actually, these two things interact with one another. Some drugs probably increase or decrease the effectiveness of cognitive behavioral therapy. In fact, we have sort of decades of neuroscience work in humans and in animals to suggest that that's the

case. So I say a very interesting avenue, and in fact, I predict a very interesting avenue in the coming years for the sort of future of mental health treatment will be a deliberate pairing of biological and psychological treatments. For example, drugs administered just before a session of therapy that will improve your ability to engage with or respond to or learn from the things happening in that therapy session. This is to some degree already happening. There are good examples in exposure therapy for people with phobias where some exposure therapy sessions are being combined with medications that increase your ability to learn from new experiences. Yeah, and I want to end on something that is, I don't know,

I thought a bit of good news when I was reading your book and that may help everyone, regardless of what mental health issues they are aren't struggling with, is that I was surprised when reading your book that it can be good for you, well, good for your mental health to do things that are a little bit bad for you. So, you know, drinking a beer, eating a cookie, or even skipping a workout, for example, it's science, right? I would say it's individual differences. We all know what works for someone doesn't necessarily work for the next person. But somehow we kind of drop this when it comes to mental health. We sit and we wait for that silver bullet that will address all mental health issues or a whole category of mental health issues like depression. or anxiety. Now, probably the most radical thing I think is that that silver bullet will never come.

We should stop thinking about that model. We should be looking towards an individual model of what works for a particular person's kind of constellation of brain, behavior, cognitive problems and how those could be intervened with with many different possible treatments, including drugs and therapy that I've mentioned, but also brain stimulation, but also lifestyle changes. And those will not necessarily be the same between people. For some people, increasing exercise is an amazing resource for their mental health. And for other people, it might actually make them feel worse. Yeah. So I will feel less guilty about not being one of those people that just feels amazing from exercising. Well, feeling less guilty is definitely good for your mental health. Absolutely. Dr. Nord, thanks so much for being on the show.

This has been a really, really phenomenal conversation. Thank you for having me. Is there a kid in your life who just can't get enough neuroscience? Check out our new free education program for kids called Hack Your Brain. Sign up at ScienceFriday.com slash hack your brain. That's ScienceFriday.com slash hack your brain. That's all the time we have for today. Lots of folks help make the show happen, including Jordan Smudjik, Charles Bergquist, George Harper, John Demkoski. Next week, how the overturn of Roe v. Wade has affected where OBGYNs decide to practice medicine. I'm SciFRI producer Shoshana Bucksbaum. Catch you next time.