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What You Should Know About Fluoride

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Wednesday, April 9, 2025

Health and Human Services Secretary Robert F. Kennedy Jr. announced on Monday that he will direct the Centers for Disease Control and Prevention to stop recommending water fluoridation nationwide “It makes no sense to have [fluoride] in our water supply,” Kennedy told reporters during a visit to Utah. “I’m very, very proud of this state for being the first state to ban it, and I hope many more will come.”But what exactly is fluoride? What does it do? And why are people like Kennedy calling for its removal from public water systems? We asked experts to break down the debate. What is fluoride? Why is it in drinking water?“Fluoride is a naturally occurring mineral that belongs to a group of chemical compounds containing the element fluorine,” said Dr. Jarrett L. Manning, a dentist and founder of JLM Dental Studio. “It exists in various forms: sodium fluoride, stannous fluoride and sodium monofluorophosphate.”Small amounts of fluoride are naturally present in soil, plants, water and certain foods, but it’s also added to drinking water and dental products due to its ability to strengthen tooth enamel and prevent cavities.“Many communities add fluoride to public water supplies, a process known as water fluoridation, to improve oral health and help prevent tooth decay on a population level,” Manning explained.Basically, acid-producing bacteria grows in the mouth, which dissolves minerals on the surface of teeth and can lead to tooth decay, or cavities. Fluoride prevents and stops that bacterial growth and can even reverse early tooth decay, thus reducing the need for treatments, which can be painful and expensive.“Research over many years has shown that water fluoridation can significantly reduce the incidence of cavities in both children and adults, regardless of access to dental care,” said Dr. Cheryline Pezzullo, a clinical associate professor and director of community-based programs at New York University’s College of Dentistry. “By adding small, safe amounts of fluoride to the water supply, communities can reduce tooth decay across the board, particularly benefiting those who may not have regular access to dental care.”Grand Rapids, Michigan, became the first city to fluoridate its public water supply, in 1945, and a decade later, the rate of cavities in local children had fallen 60% to 65%. Researchers reported similar findings among both kids and adults as more communities adopted fluoridation in the subsequent decades.Today, more than 60% of the U.S. population receives fluoridated water.“The American Dental Association has long been a proponent of water fluoridation since its introduction and study,” said cosmetic dentist Dr. Amanda Lewis. Other public health groups, such as the American Academy of Pediatrics (AAP) and the Centers for Disease Control and Prevention (CDC), similarly support this practice due to its benefits to oral and overall health. Preventing tooth decay lowers the need for treatments such as tooth extractions and fillings, and if left untreated, cavities can lead to serious abscesses, infections and even sepsis.The Public Health Service recommends a concentration of 0.7 milligram of fluoride per liter of water in community systems, which the CDC equates to about three drops of water in a 55-gallon barrel. Communities that already have naturally higher levels of fluoride do not need fluoridation.What’s the controversy?“The controversy around fluoride in water often centers on questions about health risks, personal choice and concerns about overexposure,” Pezzullo said. “Although I do not agree, some argue that fluoride ― even in small amounts ― could have potential health risks and question the ethics of adding it to public water supplies.”In recent years, communities across the U.S. have voted to stop fluoridating their water systems. Many experts believe that the anti-fluoridation movement gained more traction amid the growing mistrust of public health authorities and government overall during the COVID-19 pandemic. “Some people feel that adding fluoride to public water supplies violates their right to choose what goes into their bodies,” Manning noted.In September, a federal judge in California ruled that the Environmental Protection Agency must strengthen regulations around water fluoridation to address concerns about potential health risks, particularly with regard to children’s cognitive development. “There’s skepticism from certain groups about the long-term effects, despite decades of research showing its safety and effectiveness when used correctly,” Pezzullo said. “Additionally, misinformation and conflicting studies have created more confusion and lead to more public debate.”Many skeptics point to a review from the National Toxicology Program, which concluded “with moderate confidence” that there is an association between higher levels of fluoride exposure and lower IQ in children.But that analysis is primarily based on studies conducted in other countries and involving fluoride concentrations of 1.5 milligrams per liter of water and above ― which is more than double the recommended limit for drinking water in the U.S.“More studies are needed to fully understand the potential for lower fluoride exposure to affect children’s IQ,” the organization stated in its report.The AAP has also expressed concerns about the limitations of the NTP’s review, including the high fluoride levels but also the geographic heterogeneity of the study populations, which hinders the ability to account for other factors that might affect IQ and assess whether the data is “accurate, comparable, or generalizable.” The organization noted that similar reviews from other groups have reached different conclusions and that the National Academies of Sciences, Engineering and Medicine rejected two earlier drafts of the report.Nico De Pasquale Photography via Getty ImagesTewodros R. Godebo, an assistant professor at the Tulane University Celia Scott Weatherhead School of Public Health and Tropical Medicine who studies fluoride, told HuffPost there’s still a shortage of research on public water fluoridation in the U.S.“Before we make a policy decision to remove fluoride from U.S. public water supply systems, we need to get some questions answered,” he said. “We need more studies in the U.S. if we are going to make policy here, and the science is not yet consistent enough to make a decision.”He pointed to the lack of data on fluoridation’s effect on adults and the inconsistent conclusions about any potential association between fluoride in developed countries’ community water systems and children’s cognitive development. “If we find there is some association between IQ points and low fluoride exposure, then the next critical step would be to do a risk-benefit analysis because there is a benefit to water fluoridation in terms of dental health,” Godebo said.“What would be the cost in terms of treating dental decay and associated diseases because it’s linked to our overall health and things like heart disease. What would the total IQ loss be in a child ― would it be one point? Then is our first step to reduce water fluoridation? Do we cut that 0.7 in half? This decision has to be based on strong science.”These decisions might also have to vary on the local level in accordance with area-based data, which will likely differ across the U.S. Many fluoride studies are also limited by the challenge of accounting for other sources of fluoride exposure beyond water supply systems.Critics have argued that adding fluoride to drinking water may no longer be as effective as it was when the practice first began due to the increased use of fluoride toothpaste over time. Some point to the large number of countries that do not fluoridate their public water but have still seen reductions in tooth decay. Future data from the American communities that have removed fluoride from their systems will presumably provide more clarity.Meanwhile, misleading claims about fluoride’s potential harms have gained momentum. On Nov. 2, Kennedy asserted in a social media post that the mineral is associated with thyroid disease, arthritis and bone-related issues such as bone cancer and bone fractures.Medical experts have responded by emphasizing the lack of rigorous U.S.-based research linking fluoride to thyroid disease and arthritis. As for bone health, repeated fluoride exposure above the recommended level can lead to skeletal fluorosis, which causes weakened bones, joint pain and stiffness, but that condition is extremely rare in the U.S.Excessive fluoride exposure in children whose permanent teeth are still developing (usually up to the age of 8) can result in a cosmetic condition called dental fluorosis, which gives the teeth white spots, flecks or lines but does not cause pain or impair tooth function.To address concerns about dental fluorosis, the U.S. government amended its recommendations on public water fluoridation in 2015. Though the previous guidance recommended 0.7 milligram per liter in warmer climates and 1.2 milligrams in cooler places, the standard became 0.7 everywhere.Similarly, the ADA recommends very small amounts of fluoride toothpaste for young children to limit excess ingestion and prevent dental fluorosis. Here’s what you should know if you’re concerned about fluoride in water.Headlines can be alarming, so if you’re feeling overwhelmed by the fluoride debate taking place online and in the news, talk to your doctor, your dentist or your child’s pediatrician.“For those who are new to the topic, it’s helpful to know that fluoride has been safely added to water supplies across many parts of the world since the 1940s, with a significant decrease in cavities as a result,” Pezzullo said.She emphasized that fluoride levels in public drinking water are carefully regulated and monitored.“While it’s good to be cautious, substantial amounts of scientific research have shown that fluoride at these regulated levels is safe and does not cause harm,” Pezzullo explained. “I give fluoridated water to my own toddler and brush his teeth with fluoridated toothpaste! I can always tell when a child is not exposed to fluoride when they sit in my chair as they always have more cavities than they should.”Water fluoridation is a “simple but powerful health measure” that has been particularly beneficial for children and communities with limited access to dental care, she added. “As a dentist, I see the difference fluoride makes every day, especially in vulnerable populations.”Assessing the relative benefits and risks of water fluoridation is crucial for making policy decisions at the government level and personal choices on an individual level.Although the data has not been conclusive, preliminary research suggests that fluoride exposure during pregnancy could potentially lead to neurobehavioral issues in children. Experts who have studied this possible link are notably not calling for an end to water fluoridation, but they have suggested that pregnant women might want to opt for filtered water.“Those who prefer to avoid fluoride can choose to use fluoride-free dental products or install home water filters that remove fluoride,” Manning said. “There are alternatives to fluoride and complementary approaches for maintaining strong teeth and good oral health. Some of those alternatives are xylitol, hydroxyapatite and recaldent, just to name a few.”Lewis similarly advised reading the labels on your dental products if you want to cut down on your fluoride intake while opting for toothpastes and mouth rinses with other decay-preventing ingredients. She noted that the time and manner in which we eat, sleep and breath can also affect our oral health and thus overall health and wellness.“If you live in a city with fluoride, exposure will be inevitable,” Lewis said, listing sources like washed produce, showers and restaurant coffee, tea and water. “You can filter your water at home or purchase filtered water from a number of locations, but it is unlikely that you can completely eliminate your exposure.”It’s worth reiterating, however, that there has not been sufficient data to determine if the 0.7 milligram fluoride standard in the U.S. is linked to the health concerns critics have raised.And although Kennedy has promised to “advise all U.S. water systems to remove fluoride from public water,” the federal government ultimately cannot decide whether a community fluoridates its water supply. That decision remains at the state and local level. We Don't Work For Billionaires. We Work For You.Big money interests are running the government — and influencing the news you read. While other outlets are retreating behind paywalls and bending the knee to political pressure, HuffPost is proud to be unbought and unfiltered. Will you help us keep it that way? You can even access our stories ad-free.You've supported HuffPost before, and we'll be honest — we could use your help again. We won't back down from our mission of providing free, fair news during this critical moment. But we can't do it without you.For the first time, we're offering an ad-free experience to qualifying contributors who support our fearless journalism. We hope you'll join us.You've supported HuffPost before, and we'll be honest — we could use your help again. We won't back down from our mission of providing free, fair news during this critical moment. But we can't do it without you.For the first time, we're offering an ad-free experience to qualifying contributors who support our fearless journalism. We hope you'll join us.Support HuffPostAlready contributed? Log in to hide these messages.This story has been updated to reflect new announcements from Health and Human Services Secretary Robert F. Kennedy Jr.

Here's what medical and public health experts are saying about the debate around fluoridation of drinking water.

Health and Human Services Secretary Robert F. Kennedy Jr. announced on Monday that he will direct the Centers for Disease Control and Prevention to stop recommending water fluoridation nationwide

“It makes no sense to have [fluoride] in our water supply,” Kennedy told reporters during a visit to Utah. “I’m very, very proud of this state for being the first state to ban it, and I hope many more will come.”

But what exactly is fluoride? What does it do? And why are people like Kennedy calling for its removal from public water systems? We asked experts to break down the debate.

What is fluoride? Why is it in drinking water?

“Fluoride is a naturally occurring mineral that belongs to a group of chemical compounds containing the element fluorine,” said Dr. Jarrett L. Manning, a dentist and founder of JLM Dental Studio. “It exists in various forms: sodium fluoride, stannous fluoride and sodium monofluorophosphate.”

Small amounts of fluoride are naturally present in soil, plants, water and certain foods, but it’s also added to drinking water and dental products due to its ability to strengthen tooth enamel and prevent cavities.

“Many communities add fluoride to public water supplies, a process known as water fluoridation, to improve oral health and help prevent tooth decay on a population level,” Manning explained.

Basically, acid-producing bacteria grows in the mouth, which dissolves minerals on the surface of teeth and can lead to tooth decay, or cavities. Fluoride prevents and stops that bacterial growth and can even reverse early tooth decay, thus reducing the need for treatments, which can be painful and expensive.

“Research over many years has shown that water fluoridation can significantly reduce the incidence of cavities in both children and adults, regardless of access to dental care,” said Dr. Cheryline Pezzullo, a clinical associate professor and director of community-based programs at New York University’s College of Dentistry. “By adding small, safe amounts of fluoride to the water supply, communities can reduce tooth decay across the board, particularly benefiting those who may not have regular access to dental care.”

Grand Rapids, Michigan, became the first city to fluoridate its public water supply, in 1945, and a decade later, the rate of cavities in local children had fallen 60% to 65%. Researchers reported similar findings among both kids and adults as more communities adopted fluoridation in the subsequent decades.

Today, more than 60% of the U.S. population receives fluoridated water.

The American Dental Association has long been a proponent of water fluoridation since its introduction and study,” said cosmetic dentist Dr. Amanda Lewis.

Other public health groups, such as the American Academy of Pediatrics (AAP) and the Centers for Disease Control and Prevention (CDC), similarly support this practice due to its benefits to oral and overall health. Preventing tooth decay lowers the need for treatments such as tooth extractions and fillings, and if left untreated, cavities can lead to serious abscesses, infections and even sepsis.

The Public Health Service recommends a concentration of 0.7 milligram of fluoride per liter of water in community systems, which the CDC equates to about three drops of water in a 55-gallon barrel. Communities that already have naturally higher levels of fluoride do not need fluoridation.

What’s the controversy?

“The controversy around fluoride in water often centers on questions about health risks, personal choice and concerns about overexposure,” Pezzullo said. “Although I do not agree, some argue that fluoride ― even in small amounts ― could have potential health risks and question the ethics of adding it to public water supplies.”

In recent years, communities across the U.S. have voted to stop fluoridating their water systems. Many experts believe that the anti-fluoridation movement gained more traction amid the growing mistrust of public health authorities and government overall during the COVID-19 pandemic.

“Some people feel that adding fluoride to public water supplies violates their right to choose what goes into their bodies,” Manning noted.

In September, a federal judge in California ruled that the Environmental Protection Agency must strengthen regulations around water fluoridation to address concerns about potential health risks, particularly with regard to children’s cognitive development.

“There’s skepticism from certain groups about the long-term effects, despite decades of research showing its safety and effectiveness when used correctly,” Pezzullo said. “Additionally, misinformation and conflicting studies have created more confusion and lead to more public debate.”

Many skeptics point to a review from the National Toxicology Program, which concluded “with moderate confidence” that there is an association between higher levels of fluoride exposure and lower IQ in children.

But that analysis is primarily based on studies conducted in other countries and involving fluoride concentrations of 1.5 milligrams per liter of water and above ― which is more than double the recommended limit for drinking water in the U.S.

“More studies are needed to fully understand the potential for lower fluoride exposure to affect children’s IQ,” the organization stated in its report.

The AAP has also expressed concerns about the limitations of the NTP’s review, including the high fluoride levels but also the geographic heterogeneity of the study populations, which hinders the ability to account for other factors that might affect IQ and assess whether the data is “accurate, comparable, or generalizable.” The organization noted that similar reviews from other groups have reached different conclusions and that the National Academies of Sciences, Engineering and Medicine rejected two earlier drafts of the report.

Nico De Pasquale Photography via Getty Images

Tewodros R. Godebo, an assistant professor at the Tulane University Celia Scott Weatherhead School of Public Health and Tropical Medicine who studies fluoride, told HuffPost there’s still a shortage of research on public water fluoridation in the U.S.

“Before we make a policy decision to remove fluoride from U.S. public water supply systems, we need to get some questions answered,” he said. “We need more studies in the U.S. if we are going to make policy here, and the science is not yet consistent enough to make a decision.”

He pointed to the lack of data on fluoridation’s effect on adults and the inconsistent conclusions about any potential association between fluoride in developed countries’ community water systems and children’s cognitive development.

“If we find there is some association between IQ points and low fluoride exposure, then the next critical step would be to do a risk-benefit analysis because there is a benefit to water fluoridation in terms of dental health,” Godebo said.

“What would be the cost in terms of treating dental decay and associated diseases because it’s linked to our overall health and things like heart disease. What would the total IQ loss be in a child ― would it be one point? Then is our first step to reduce water fluoridation? Do we cut that 0.7 in half? This decision has to be based on strong science.”

These decisions might also have to vary on the local level in accordance with area-based data, which will likely differ across the U.S. Many fluoride studies are also limited by the challenge of accounting for other sources of fluoride exposure beyond water supply systems.

Critics have argued that adding fluoride to drinking water may no longer be as effective as it was when the practice first began due to the increased use of fluoride toothpaste over time. Some point to the large number of countries that do not fluoridate their public water but have still seen reductions in tooth decay. Future data from the American communities that have removed fluoride from their systems will presumably provide more clarity.

Meanwhile, misleading claims about fluoride’s potential harms have gained momentum. On Nov. 2, Kennedy asserted in a social media post that the mineral is associated with thyroid disease, arthritis and bone-related issues such as bone cancer and bone fractures.

Medical experts have responded by emphasizing the lack of rigorous U.S.-based research linking fluoride to thyroid disease and arthritis. As for bone health, repeated fluoride exposure above the recommended level can lead to skeletal fluorosis, which causes weakened bones, joint pain and stiffness, but that condition is extremely rare in the U.S.

Excessive fluoride exposure in children whose permanent teeth are still developing (usually up to the age of 8) can result in a cosmetic condition called dental fluorosis, which gives the teeth white spots, flecks or lines but does not cause pain or impair tooth function.

To address concerns about dental fluorosis, the U.S. government amended its recommendations on public water fluoridation in 2015. Though the previous guidance recommended 0.7 milligram per liter in warmer climates and 1.2 milligrams in cooler places, the standard became 0.7 everywhere.

Similarly, the ADA recommends very small amounts of fluoride toothpaste for young children to limit excess ingestion and prevent dental fluorosis.

Here’s what you should know if you’re concerned about fluoride in water.

Headlines can be alarming, so if you’re feeling overwhelmed by the fluoride debate taking place online and in the news, talk to your doctor, your dentist or your child’s pediatrician.

“For those who are new to the topic, it’s helpful to know that fluoride has been safely added to water supplies across many parts of the world since the 1940s, with a significant decrease in cavities as a result,” Pezzullo said.

She emphasized that fluoride levels in public drinking water are carefully regulated and monitored.

“While it’s good to be cautious, substantial amounts of scientific research have shown that fluoride at these regulated levels is safe and does not cause harm,” Pezzullo explained. “I give fluoridated water to my own toddler and brush his teeth with fluoridated toothpaste! I can always tell when a child is not exposed to fluoride when they sit in my chair as they always have more cavities than they should.”

Water fluoridation is a “simple but powerful health measure” that has been particularly beneficial for children and communities with limited access to dental care, she added. “As a dentist, I see the difference fluoride makes every day, especially in vulnerable populations.”

Assessing the relative benefits and risks of water fluoridation is crucial for making policy decisions at the government level and personal choices on an individual level.

Although the data has not been conclusive, preliminary research suggests that fluoride exposure during pregnancy could potentially lead to neurobehavioral issues in children. Experts who have studied this possible link are notably not calling for an end to water fluoridation, but they have suggested that pregnant women might want to opt for filtered water.

“Those who prefer to avoid fluoride can choose to use fluoride-free dental products or install home water filters that remove fluoride,” Manning said. “There are alternatives to fluoride and complementary approaches for maintaining strong teeth and good oral health. Some of those alternatives are xylitol, hydroxyapatite and recaldent, just to name a few.”

Lewis similarly advised reading the labels on your dental products if you want to cut down on your fluoride intake while opting for toothpastes and mouth rinses with other decay-preventing ingredients. She noted that the time and manner in which we eat, sleep and breath can also affect our oral health and thus overall health and wellness.

“If you live in a city with fluoride, exposure will be inevitable,” Lewis said, listing sources like washed produce, showers and restaurant coffee, tea and water. “You can filter your water at home or purchase filtered water from a number of locations, but it is unlikely that you can completely eliminate your exposure.”

It’s worth reiterating, however, that there has not been sufficient data to determine if the 0.7 milligram fluoride standard in the U.S. is linked to the health concerns critics have raised.

And although Kennedy has promised to “advise all U.S. water systems to remove fluoride from public water,” the federal government ultimately cannot decide whether a community fluoridates its water supply. That decision remains at the state and local level.

We Don't Work For Billionaires. We Work For You.

Big money interests are running the government — and influencing the news you read. While other outlets are retreating behind paywalls and bending the knee to political pressure, HuffPost is proud to be unbought and unfiltered. Will you help us keep it that way? You can even access our stories ad-free.

You've supported HuffPost before, and we'll be honest — we could use your help again. We won't back down from our mission of providing free, fair news during this critical moment. But we can't do it without you.

For the first time, we're offering an ad-free experience to qualifying contributors who support our fearless journalism. We hope you'll join us.

You've supported HuffPost before, and we'll be honest — we could use your help again. We won't back down from our mission of providing free, fair news during this critical moment. But we can't do it without you.

For the first time, we're offering an ad-free experience to qualifying contributors who support our fearless journalism. We hope you'll join us.

Support HuffPost

Already contributed? Log in to hide these messages.

This story has been updated to reflect new announcements from Health and Human Services Secretary Robert F. Kennedy Jr.

Read the full story here.
Photos courtesy of

As oil and gas companies pivot to plastic, California neighborhoods become sacrifice zones again

As oil and gas companies pivot to plastic, certain California neighborhoods become unhealthy sacrifice zones again.

Guest Commentary written by Veronica Herrera Veronica Herrera is a professor of urban planning at UCLA Daniel Coffee Daniel Coffee is a researcher at UCLA’s Luskin Center for Innovation The fossil fuel industry is pivoting. As demand for gasoline declines, oil and gas companies are betting their future on plastic. What once powered our cars is now being refined, cracked and polymerized into bottles, packaging and single-use products that will outlive us all. This shift isn’t just a climate concern — it’s a public health crisis. Plastics are fossil fuels in another form. And the communities most exposed to their production bear the highest health burdens. A new report from the UCLA Luskin Center for Innovation on what defines a plastic-burdened community traces how this expanding plastic economy maps directly onto California’s oil and gas footprint.  Even as California celebrates its climate leadership, our neighborhoods remain entwined with the legacies of fossil fuel infrastructure. More than 2.5 million Californians live within a kilometer of an active or idle oil or gas well. There are pumpjacks in Inglewood, refineries along the Wilmington corridor and wells beside schools in Kern County.  Refinery infrastructure — much of it feeding plastic precursor production — also is heavily concentrated in Los Angeles County, the most populous region in the state. Unequal exposure The science is unequivocal: living near oil and gas development is linked to a wide array of health harms: respiratory disease, cardiovascular illness, adverse birth outcomes and elevated cancer risk. The higher odds for these conditions persist even when controlling for socioeconomic and environmental factors.  In California and beyond, research shows pollutants from drilling and refining — such as volatile organic compounds, nitrogen oxides, particulate matter and formaldehyde — degrade air quality and increase asthma, heart attack and low-birth-weight rates. The burden of these exposures falls unevenly, our analysis shows.  Neighborhoods closest to wells and refineries have far higher proportions of Latino and Black residents, lower incomes and greater health vulnerabilities. On average, for each refinery within 1.5 miles of a community, the median household income is nearly $11,000 lower, poverty rates are 5.5% higher and emergency-room visits for asthma and heart disease are significantly elevated.  The environmental injustices of the oil age are being repackaged in the plastic economy. Globally, the Organisation for Economic Co-operation and Development projects plastic production will triple by 2060. Petrochemicals already account for roughly 14% of oil use and by mid-century could drive nearly half of global oil demand. In other words, even as we transition away from burning fossil fuels, we are locking ourselves into new forms of dependence — embedded in the packaging we discard daily. Recognizing this link is critical as California prepares to implement the Plastic Pollution Mitigation Fund under Senate Bill 54, a plastics recycling and pollution prevention law signed in 2022. The fund will direct hundreds of millions of dollars from the plastics industry to communities harmed by pollution.  Administered wisely, the fund could be a catalyst for mitigating the adverse health impacts of plastics and could create a transformative shift away from plastic production, use and disposability, building on the plastic reduction efforts required of the industry under SB 54. Plastic pollution is not just about littered beaches or overflowing landfills; it begins long before a product reaches a store shelf.  If California truly intends to lead on climate and environmental justice, it must see plastic for what it is — the fossil fuel industry’s new frontier — and it must ensure that communities long treated as sacrifice zones become the first to benefit from solutions.

Interoception Is Our Sixth Sense, and It May Be Key to Mental Health

Disruptions in interoception may underlie anxiety, eating disorders, and other mental health ailments

By the time Maggie May, an Arkansas resident in her 30s, was admitted to a psychiatric clinic in 2024, she had been struggling for years with atypical anorexia nervosa, an eating disorder that leads to severe food restriction and profound disturbances in body image. (Her name has been changed for privacy.) She had already tried traditional interventions with a psychotherapist and a dietitian, but they had failed to improve her condition. So when May heard about a trial of a new and unconventional therapy, she jumped at the opportunity.The treatment was unusual in that alongside talk therapy, May underwent several sessions in a sensory-deprivation chamber: a dark, soundproof room where she floated in a shallow pool of water heated to match the temperature of her skin and saturated with Epsom salts to make her more buoyant. The goal was to blunt May’s external senses, enabling her to feel from within—focusing on the steady thudding of her heart, the gentle flow of air in and out of her lungs, and other internal bodily signals.The ability to connect with the body’s inner signals is called interoception. Some people are better at it than others, and one’s aptitude for it may change. Life events can also bolster or damage a person’s interoceptive skills. Sahib Khalsa, a psychiatrist and neuroscientist at the University of California, Los Angeles, and his colleagues think a disrupted interoception system might be one of the driving forces behind anorexia nervosa. So they decided to repurpose a decades-old therapy called flotation-REST (for “reduced environmental stimulation therapy”) and launched a trial with it in 2018. They hypothesized that in people with anorexia and some other disorders, an underreliance on internal signals may lead to an overreliance on external ones, such as how one looks in the mirror, that ultimately causes distorted body image, one of the key factors underlying these conditions. “When they’re in the float environment, they experience internal signals more strongly,” Khalsa says. “And having that experience may then confer a different understanding of the brain-body relationship that they have.”On supporting science journalismIf you're enjoying this article, consider supporting our award-winning journalism by subscribing. By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today.Studies have implicated problems with this inner sense in a wide variety of conditions, including anxiety disorders, post-traumatic stress disorder and borderline personality disorder. Some researchers and clinicians now think that problems in interoception might contribute to many mental illnesses. Alongside this research, which itself is complicated by challenges in testing design and by a less than clear understanding of interoception, other groups are also developing therapies that aim to target this inner sense and boost psychological well-being.This work is circling in on a central message: the body and mind are inextricably intertwined. “We have always thought about [mental health conditions] as being in the brain or the mind,” says Camilla Nord, a professor of cognitive neuroscience at the University of Cambridge. But clinicians have long noted that people with mental illness frequently report physical symptoms such as abnormalities in heartbeats, breathing and appetite, she adds.The idea that the body can influence the mind dates back centuries. In the 1800s two psychologists on opposite ends of the globe independently proposed a then novel idea: emotions are the result of bodily reactions to a specific event. Called the James-Lange theory after its founders, American psychologist William James and Danish doctor Carl Lange, this view ran counter to the long-dominant belief that emotions were the cause, not a consequence, of corresponding physiological changes.Although this notion has garnered critics, it inspired a slew of studies. The 1980s saw a surge of interest in the role of physiological signals in panic disorders. Researchers discovered that they could bring on panic attacks by asking people to inhale carbon dioxide–enriched air, which can increase breathing rates, or by injecting them with isoproterenol, a drug that increases heart rate.Breathing rate can affect how someone perceives the intensity and unpleasantness of pain.These findings led some psychologists to suggest that physical sensations were the primary trigger of panic attacks. In the early 1990s Anke Ehlers, a psychologist then at the University of Göttingen in Germany, and her team examined dozens of people with panic disorders and reported that these patients were better able to perceive their heartbeats than healthy individuals—and that this greater awareness was linked to more severe symptoms. On top of that, a small, preliminary study by Ehlers of 17 patients revealed that those who were more skilled at this task were more likely to relapse and start having panic attacks again. These observations hinted at a two-way dynamic: not only could physical sensations within the body cause psychological effects, but the ability to perceive and interpret those signals—in other words, one’s interoceptive ability—could have a profound influence on mental health.Over the years a growing body of evidence has indicated that interoception plays an important role in shaping both emotions and psychological health. A large chunk of this work has focused on the heart. With every heartbeat, blood rushes into the arteries and triggers sensors known as baroreceptors, which shoot off messages to the brain conveying information about how strongly and rapidly the heart is beating.In one pivotal 2014 study, Hugo Critchley, a neuropsychiatrist at Brighton and Sussex Medical School in England, and his team reported that this process can affect a person’s sensitivity to fear. By monitoring volunteers’ heartbeats while they viewed fearful or neutral faces, they found that people detected fearful faces more easily and judged them as more intense when their heart was pumping out blood than when it was relaxing and refilling. But participants with higher levels of anxiety often perceived fear even when their hearts relaxed.Researchers have also demonstrated that bodily signals such as breathing patterns and gut rhythms can influence emotional reactions. People are quicker to react to fearful faces while breathing in than while breathing out, and breathing rate can affect how someone perceives the intensity and unpleasantness of pain.In more recent work, some neuroscientists have turned their attention to the gastrointestinal system. In 2021 Nord and her colleagues discovered that people given a dose of an antinausea drug that affects gut rhythms—processes within the stomach that help digestion—were less likely to look away from pictures of feces than they normally would have been. These disgust-related visceral signals, Nord speculates, may be relevant to eating disorders. “It’s possible that some of these signals contribute to feeling aversion to signals of satiety, making satiety very uncomfortable, a feeling you don’t want to feel,” she says.But how, exactly, do disruptions in interoception come about? Many researchers suspect it may have to do with our brain’s predictions going awry. Interoception, like our other senses, feeds information to the brain, which some neuroscientists suggest is a prediction machine: it constantly uses our prior knowledge of the world to make inferences about incoming signals. In the case of interoception, the brain attempts to decode the cause of internal sensations. If its interpretations are incorrect, they may lead to negative psychological effects—for example, if a person erroneously assumes their heart rate is elevated, they may begin to feel anxious in the absence of a threat. And if a person has learned to associate pangs of hunger with disgust, they might severely restrict how much food they consume.Inner signals can be much more ambiguous than the external input from other senses such as sight and hearing. So the brain’s prior information about these internal signals becomes especially important, says André Schulz, a professor of psychology at the University of Luxembourg.To better understand and assess potential mismatches in subjective and objective measures of our bodily signals, researchers have developed a framework that captures the different dimensions in which interoceptive processing occurs. In 2015 Sarah Garfinkel, then a postdoctoral researcher in Critchley’s group at Brighton and Sussex, and her colleagues proposed a model to clearly differentiate three categories of interoceptive processing: interoceptive accuracy (how well someone performs, objectively, on relevant tasks such as heartbeat detection), interoceptive sensibility (a person’s subjective evaluation of their interoceptive abilities), and interoceptive awareness (how well that self-assessment matches their actual abilities).Along with their collaborators, Garfinkel, now at University College London, and Critchley have found that in autistic adults there is a link between anxiety and a poor ability to predict one’s interoceptive skill—in this case, one’s sensitivity to heartbeat. In a study of 40 people (20 of whom had autism), they and their colleagues discovered that individuals with autism performed worse on a heartbeat-detection task and were more likely to overestimate their interoceptive abilities than those without autism. This disconnect was more pronounced in people with higher levels of anxiety, suggesting that errors in the ability to predict bodily signals may contribute to feelings of anxiety, Critchley says.In recent years the list of psychiatric conditions linked to interoceptive dysfunctions has grown. Some, such as panic and anxiety disorders, are associated with heightened attention to one’s internal processes; others, such as borderline personality disorder and schizophrenia, may be tied to a blunting of one’s ability to connect with these signals. In a review of interoception research, published in 2021, Nord and her colleagues examined 33 studies that collectively involved more than 1,200 participants. They found that people with a range of psychiatric disorders, including anxiety disorders and schizophrenia, shared similar alterations in the insula, a key brain region linked with interoception during body-sensing-related tasks.Overall, though, studies show mixed results. “If you look across the literature, [however many] studies have found an association with, say, anxiety, [a roughly] equal amount will have not found a relationship or found it in the other direction,” says Jennifer Murphy, a psychologist at the University of Surrey in England.The varying results could stem from the challenges associated with studying interoception, which can be difficult to both manipulate and measure. Take cardiac interoception. In most early studies in this domain, participants counted their pulses, but this test may measure people’s estimate of their heart rate rather than how well they can feel their heartbeat. This flaw was perhaps most clearly demonstrated in a 1999 study in which people with pacemakers reported their heart rates while experimenters (with the participants’ consent) secretly tuned their pacemakers’ timing up or down. Participants’ self-reported heart rates didn’t follow the shifts in the actual pulses; their beliefs about how their heart rates should be changing had a much stronger influence.To address these limitations, scientists have been devising better study methods. Micah Allen, a neuroscientist at Aarhus University in Denmark, and his team have developed a heart-rate-discrimination task in which people are asked to report whether a series of tones is faster or slower than their current pulse, allowing researchers to quantify how sensitive an individual is to their heartbeats. Allen and his colleagues are now testing breath interoception in a similar way. Using a computer-controlled device, the researchers can make precise changes to the air resistance someone feels when they inhale through a tube. By doing so, they can quantify how well the person can detect changes in their breathing.Using these new techniques, Allen’s team has learned that an individual’s interoceptive chops don’t translate across all domains. In a recent preprint study of 241 people, they found that a person’s ability to perceive their heart rate wasn’t correlated to their performance in a breathing-resistance task.Researchers have also been combining these behavioral tests with measurements of brain activity. One example is the heartbeat-evoked potential, a spike in brain signaling that occurs each time the heart beats. Scientists have found that changes in these signals, which can be detected with noninvasive brain-imaging techniques such as electroencephalography, are linked to accuracy in heartbeat-detection tasks and to the ability to process emotions. Similar brain signals related to organs such as the gut and those of the respiratory system have been linked to the ability to perceive sensations within those organs.These studies indicate that interoception abilities don’t align across a person’s bodily functions, from breathing to heart rate to gut rhythms. It’s therefore difficult to know whether the conflicting findings about the role of interoception disruptions in mental disorders mean there is no meaningful relation to be found or whether the issue is that researchers have simply not been using the right task or studying the most relevant system or level of interoception, Murphy says. “It’s very unlikely that every condition will have the same bit of interoception disrupted.”Untangling how, exactly, interoception is disrupted in people with mental illness remains an active area of investigation. Some experts say answers may come from treatment trials investigating whether interventions that target disturbances in this inner sense might boost mental health. Many such studies are currently underway.“To understand what interoception is, we need to manipulate it,” Allen says. “And to understand its role as a biomarker, as something that is related to mental health, we also need to manipulate it.”Jane Green knows stressful situations can have immediate effects on her body. For Green, who has autism, reading a piece of bad news or dealing with a face-to-face confrontation may set off a chain reaction in her body: a rush of adrenaline followed by a pounding heart, bloating and itchiness, among other physical reactions.Such responses may be linked to an inability to read one’s inner body. In 2019 she took part in a clinical trial in which Critchley, Garfinkel and their colleagues sought to test just that—how resolving a discrepancy between a person’s perceived interoceptive abilities and reality could improve anxiety levels in adults with autism spectrum disorder. The intervention in the study focused on tasks that involved heartbeat detection.After training and testing 121 participants (half of whom were randomly assigned to receive a noninteroception-based control task) across six sessions, the team reported in a 2021 paper that this treatment successfully reduced anxiety in their participants and that this effect persisted for at least three months.Participating in the trial was a “real turning point” in Green’s ability to deal with anxiety, she says. “I recognize now that when I’m stressed, whether I like it or not, my body reacts,” she explains. Although she still experiences physical reactions to emotionally charged situations, they are often less severe than they were prior to the treatment. And her knowledge of what’s happening in her body has made it easier to cope, she adds. Green is chair and founder of SEDSConnective, a charity dedicated to neurodivergent people with connective tissue disorders such as Ehlers-Danlos syndromes. These conditions tend to overlap with anxiety disorders, and Green is now advocating for interoception-based therapies to help affected people.A person’s interoceptive capabilities might be especially malleable during early childhood or adolescence.For May, who participated in the flotation-REST trial, what she learned from being cut off from the external world helped her to get through an inpatient stay at an eating-disorder clinic where she was being forced to eat—and, as a result, gain weight. “You’re working on the things that drove you to come in the first place, but at the same time, your distress with your body is getting worse and worse,” she says. When she was in the flotation chamber, however, May’s awareness of her physical body would slip away, reducing some of the negative feelings she had about herself and quieting the worries that swirled in her mind. “You can’t tell where your body stops and the water begins,” May says. “Because you’re completely buoyant, you also have no sense of the ways that your body distresses you.”Flotation-REST shows promise: in a clinical trial of 68 people hospitalized for anorexia nervosa who were randomly assigned to the therapy or a placebo, Khalsa’s team found that six months after treatment, those who received therapy reported less body dissatisfaction than those who did not. The researchers have also created a version of this therapy for anxiety and depression. In early-stage clinical trials, this intervention appeared to reduce the symptoms of those disorders. Now they are investigating whether this therapy might also benefit people with amphetamine use disorder.Other interoception-based treatments are also under investigation. At Emory University, a group led by clinical psychologist Negar Fani has been examining the effects of combining a mindfulness-based intervention with a wearable device that delivers vibrations corresponding to a person’s breaths. In a group of trauma-exposed individuals, this intervention increased the participants’ confidence in their bodily signals more than the mindfulness-based intervention alone. Even long after these sessions, people report being able to recall the feeling of breath-synced vibrations, Fani says. “It helps to ground them, brings them back into the present moment. They can access their body signals and figure out what they want to do with them.” The team is now conducting a follow-up study to see whether this treatment can improve mental well-being in people who have experienced trauma.In yet another ongoing trial, Nord is collaborating with Garfinkel on a series of studies aimed at understanding in which body systems—and in which of the three dimensions (accuracy, sensibility and awareness)—interoception is altered in people with various mental disorders, among them anxiety and depression. As part of that effort, the researchers are testing interventions, including interoceptive training, mindfulness therapy—to help improve the mind-body connection—and stimulation of the insula with focused ultrasound.Scientists still have plenty of questions to answer about interoception. One major open question is how differences in interoception arise. Some of our interoceptive abilities may begin taking shape during early infanthood. Scientists have discovered that babies as young as three months show differences in the amount of time they spend looking at colored shapes moving either in or out of sync with their heartbeats—a finding that suggests our ability to sense heart rhythms is present at this young age.Interactions with caregivers during one’s first years may play a crucial role in determining how in tune a person becomes with their body. The way a parent responds to an infant’s cues about being hungry, tired or in pain, for instance, may shape how well the child is able to interpret those signals later in life. Although direct evidence for this hypothesis is still lacking, studies have shown that an individual’s early caregiving environment can shape how their body responds to stress.Other factors such as a person’s sex or various environmental conditions, including adversity in early life, may also influence how interoception develops. Some research suggests that adverse experiences, especially chronic, interpersonal trauma early in life, may be key contributors. Clinicians have long observed that traumatic events can lead people to detach or “dissociate” from the body, and some researchers have proposed that this disconnect can disrupt interoceptive processes over time. For a subset of people, these alterations might be linked to an increased likelihood of self-harm and suicide: one 2020 study, for example, found that people with a history of suicide attempts and a diagnosed mental illness, such as anxiety, PTSD or depression, were worse at an interoceptive heartbeat-detection task than those who had the same ailments but had not attempted to take their own life.A person’s interoceptive abilities may change over time. Interoceptive capabilities might be especially malleable during certain life stages: periods such as early childhood, when a person is just learning how to interpret their bodily signals, or adolescence, when puberty is creating a whirlwind of physical changes. It might be one mechanism, among many, that explains why “these times tend to be risk periods for the development of mental illness,” Murphy says.The boundaries of interoception are also only beginning to be understood. In recent years some scientists have become interested in probing the links between the immune system and the brain, which are in constant conversation. An emerging body of work suggests that the brain both keeps tabs on and influences what happens in the immune system, and the immune system can in turn affect the brain. Studies have linked dysfunction in the immune system—namely, inflammation—to mental illnesses such as depression, psychosis and trauma-related disorders. The immune system may affect our mental states over much longer time scales than, say, the heart, which can influence our emotional experiences in real time.Understanding the mysteries of interoception may lead to better therapies for illnesses of the mind—and the body. Some researchers believe that understanding interoception may ultimately be helpful for treating physical symptoms as well. Schulz and his team, for instance, are currently evaluating interoception-based treatments for chronic fatigue syndrome (also known as myalgic encephalomyelitis), a complicated disorder that causes a range of symptoms, including severe tiredness. “Interoception has so much relevance to health in general,” Fani says. “We can’t ignore it anymore.”IF YOU NEED HELPIf you or someone you know is struggling or having thoughts of suicide, help is available. Call or text the 988 Suicide & Crisis Lifeline at 988 or use the online Lifeline Chat at chat.988lifeline.org.

Deep-learning model predicts how fruit flies form, cell by cell

The approach could apply to more complex tissues and organs, helping researchers to identify early signs of disease.

During early development, tissues and organs begin to bloom through the shifting, splitting, and growing of many thousands of cells.A team of MIT engineers has now developed a way to predict, minute by minute, how individual cells will fold, divide, and rearrange during a fruit fly’s earliest stage of growth. The new method may one day be applied to predict the development of more complex tissues, organs, and organisms. It could also help scientists identify cell patterns that correspond to early-onset diseases, such as asthma and cancer.In a study appearing today in the journal Nature Methods, the team presents a new deep-learning model that learns, then predicts, how certain geometric properties of individual cells will change as a fruit fly develops. The model records and tracks properties such as a cell’s position, and whether it is touching a neighboring cell at a given moment.The team applied the model to videos of developing fruit fly embryos, each of which starts as a cluster of about 5,000 cells. They found the model could predict, with 90 percent accuracy, how each of the 5,000 cells would fold, shift, and rearrange, minute by minute, during the first hour of development, as the embryo morphs from a smooth, uniform shape into more defined structures and features.“This very initial phase is known as gastrulation, which takes place over roughly one hour, when individual cells are rearranging on a time scale of minutes,” says study author Ming Guo, associate professor of mechanical engineering at MIT. “By accurately modeling this early period, we can start to uncover how local cell interactions give rise to global tissues and organisms.”The researchers hope to apply the model to predict the cell-by-cell development in other species, such zebrafish and mice. Then, they can begin to identify patterns that are common across species. The team also envisions that the method could be used to discern early patterns of disease, such as in asthma. Lung tissue in people with asthma looks markedly different from healthy lung tissue. How asthma-prone tissue initially develops is an unknown process that the team’s new method could potentially reveal.“Asthmatic tissues show different cell dynamics when imaged live,” says co-author and MIT graduate student Haiqian Yang. “We envision that our model could capture these subtle dynamical differences and provide a more comprehensive representation of tissue behavior, potentially improving diagnostics or drug-screening assays.”The study’s co-authors are Markus Buehler, the McAfee Professor of Engineering in MIT’s Department of Civil and Environmental Engineering; George Roy and Tomer Stern of the University of Michigan; and Anh Nguyen and Dapeng Bi of Northeastern University.Points and foamsScientists typically model how an embryo develops in one of two ways: as a point cloud, where each point represents an individual cell as point that moves over time; or as a “foam,” which represents individual cells as bubbles that shift and slide against each other, similar to the bubbles in shaving foam.Rather than choose between the two approaches, Guo and Yang embraced both.“There’s a debate about whether to model as a point cloud or a foam,” Yang says. “But both of them are essentially different ways of modeling the same underlying graph, which is an elegant way to represent living tissues. By combining these as one graph, we can highlight more structural information, like how cells are connected to each other as they rearrange over time.”At the heart of the new model is a “dual-graph” structure that represents a developing embryo as both moving points and bubbles. Through this dual representation, the researchers hoped to capture more detailed geometric properties of individual cells, such as the location of a cell’s nucleus, whether a cell is touching a neighboring cell, and whether it is folding or dividing at a given moment in time.As a proof of principle, the team trained the new model to “learn” how individual cells change over time during fruit fly gastrulation.“The overall shape of the fruit fly at this stage is roughly an ellipsoid, but there are gigantic dynamics going on at the surface during gastrulation,” Guo says. “It goes from entirely smooth to forming a number of folds at different angles. And we want to predict all of those dynamics, moment to moment, and cell by cell.”Where and whenFor their new study, the researchers applied the new model to high-quality videos of fruit fly gastrulation taken by their collaborators at the University of Michigan. The videos are one-hour recordings of developing fruit flies, taken at single-cell resolution. What’s more, the videos contain labels of individual cells’ edges and nuclei — data that are incredibly detailed and difficult to come by.“These videos are of extremely high quality,” Yang says. “This data is very rare, where you get submicron resolution of the whole 3D volume at a pretty fast frame rate.”The team trained the new model with data from three of four fruit fly embryo videos, such that the model might “learn” how individual cells interact and change as an embryo develops. They then tested the model on an entirely new fruit fly video, and found that it was able to predict with high accuracy how most of the embryo’s 5,000 cells changed from minute to minute.Specifically, the model could predict properties of individual cells, such as whether they will fold, divide, or continue sharing an edge with a neighboring cell, with about 90 percent accuracy.“We end up predicting not only whether these things will happen, but also when,” Guo says. “For instance, will this cell detach from this cell seven minutes from now, or eight? We can tell when that will happen.”The team believes that, in principle, the new model, and the dual-graph approach, should be able to predict the cell-by-cell development of other multiceullar systems, such as more complex species, and even some human tissues and organs. The limiting factor is the availability of high-quality video data.“From the model perspective, I think it’s ready,” Guo says. “The real bottleneck is the data. If we have good quality data of specific tissues, the model could be directly applied to predict the development of many more structures.”This work is supported, in part, by the U.S. National Institutes of Health.

Ignore the Influencers: Simple Showers Are Still Best

By Carole Tanzer Miller HealthDay ReporterSATURDAY, Dec. 13, 2025 (HealthDay News) — Listen to the influencers, skin-care specialists say, and your...

By Carole Tanzer Miller HealthDay ReporterSATURDAY, Dec. 13, 2025 (HealthDay News) — Listen to the influencers, skin-care specialists say, and your daily shower could do more harm than good."Your skin is a barrier," said Dr. Nicole Negbenebor, a dermatologic surgeon at University of Iowa Health Care, told The Associated Press. "So you want to treat it right, and then sometimes there can be too much of a good thing."If you’re double-cleansing, exfoliating, piling on scented body rubs and shower oils and spending a lot of time in the water, you’re probably going overboard, she and other skin-care experts agree.A daily shower with lukewarm water and hypoallergenic cleanser — preferably one that’s fragrance-free, and a slather of lotion or oil afterward are all you need, they say.Here’s a guide from dermatologists to sudsing up without getting carried away:Pay attention to time and temperature. Staying in the shower too long or cranking the temperature up too high can strip away natural oils your skin needs. The upshot: You’ll be dry and irritated.Pick the right soap. Choose one, dermatologists suggest, for sensitive skin and avoid antibacterial soaps, which can cause dryness. (Antibacterial soaps can, however, be beneficial for folks with hidradenitis suppurativa, an autoimmune condition that causes abscesses and boils on the skin, they point out.)Despite the influencers, double-cleansing isn’t necessary. No need, doctors say, to use oil-based cleansers to break down makeup and excess oil and then a water-based cleanser to remove any residue. And, they add, you sure don’t need to do that to your whole body."People overuse soap all the time," Dr. Olga Bunimovich, an assistant professor of dermatology at the University of Pittsburgh, told The AP. "You should not be soaping up all of your skin period." Instead, she advised, use soap to wash skin folds and your privates.Oil up. Once you’re out of the shower but still damp, an oil will lock in moisture that hydrates the skin, Negbenebor said. Just remember: Oil itself is a sealant, not a moisturizer.Don’t go overboard with exfoliating. Using a body scrub or loofah to remove dead cells is good for the skin, but not every day, especially if you have dry skin, acne or eczema. Using products that contain lactic or glycolic acid is a gentler way to exfoliate — but not all the time.While you’re being kind to your skin, think about the environment, too. Nearly 17% of U.S. indoor water use is in the shower, according to the U.S. Environmental Protection Agency. Shorter showers are good for the earth — and a lukewarm one that lasts long enough to clean your body should be sufficient most of the time.The University of Nebraska-Lincoln has more about showering.SOURCE: The Associated Press, July 10, 2025Copyright © 2025 HealthDay. All rights reserved.

New method improves the reliability of statistical estimations

The technique can help scientists in economics, public health, and other fields understand whether to trust the results of their experiments.

Let’s say an environmental scientist is studying whether exposure to air pollution is associated with lower birth weights in a particular county.They might train a machine-learning model to estimate the magnitude of this association, since machine-learning methods are especially good at learning complex relationships.Standard machine-learning methods excel at making predictions and sometimes provide uncertainties, like confidence intervals, for these predictions. However, they generally don’t provide estimates or confidence intervals when determining whether two variables are related. Other methods have been developed specifically to address this association problem and provide confidence intervals. But, in spatial settings, MIT researchers found these confidence intervals can be completely off the mark.When variables like air pollution levels or precipitation change across different locations, common methods for generating confidence intervals may claim a high level of confidence when, in fact, the estimation completely failed to capture the actual value. These faulty confidence intervals can mislead the user into trusting a model that failed.After identifying this shortfall, the researchers developed a new method designed to generate valid confidence intervals for problems involving data that vary across space. In simulations and experiments with real data, their method was the only technique that consistently generated accurate confidence intervals.This work could help researchers in fields like environmental science, economics, and epidemiology better understand when to trust the results of certain experiments.“There are so many problems where people are interested in understanding phenomena over space, like weather or forest management. We’ve shown that, for this broad class of problems, there are more appropriate methods that can get us better performance, a better understanding of what is going on, and results that are more trustworthy,” says Tamara Broderick, an associate professor in MIT’s Department of Electrical Engineering and Computer Science (EECS), a member of the Laboratory for Information and Decision Systems (LIDS) and the Institute for Data, Systems, and Society, an affiliate of the Computer Science and Artificial Intelligence Laboratory (CSAIL), and senior author of this study.Broderick is joined on the paper by co-lead authors David R. Burt, a postdoc, and Renato Berlinghieri, an EECS graduate student; and Stephen Bates an assistant professor in EECS and member of LIDS. The research was recently presented at the Conference on Neural Information Processing Systems.Invalid assumptionsSpatial association involves studying how a variable and a certain outcome are related over a geographic area. For instance, one might want to study how tree cover in the United States relates to elevation.To solve this type of problem, a scientist could gather observational data from many locations and use it to estimate the association at a different location where they do not have data.The MIT researchers realized that, in this case, existing methods often generate confidence intervals that are completely wrong. A model might say it is 95 percent confident its estimation captures the true relationship between tree cover and elevation, when it didn’t capture that relationship at all.After exploring this problem, the researchers determined that the assumptions these confidence interval methods rely on don’t hold up when data vary spatially.Assumptions are like rules that must be followed to ensure results of a statistical analysis are valid. Common methods for generating confidence intervals operate under various assumptions.First, they assume that the source data, which is the observational data one gathered to train the model, is independent and identically distributed. This assumption implies that the chance of including one location in the data has no bearing on whether another is included. But, for example, U.S. Environmental Protection Agency (EPA) air sensors are placed with other air sensor locations in mind.Second, existing methods often assume that the model is perfectly correct, but this assumption is never true in practice. Finally, they assume the source data are similar to the target data where one wants to estimate.But in spatial settings, the source data can be fundamentally different from the target data because the target data are in a different location than where the source data were gathered.For instance, a scientist might use data from EPA pollution monitors to train a machine-learning model that can predict health outcomes in a rural area where there are no monitors. But the EPA pollution monitors are likely placed in urban areas, where there is more traffic and heavy industry, so the air quality data will be much different than the air quality data in the rural area.In this case, estimates of association using the urban data suffer from bias because the target data are systematically different from the source data.A smooth solutionThe new method for generating confidence intervals explicitly accounts for this potential bias.Instead of assuming the source and target data are similar, the researchers assume the data vary smoothly over space.For instance, with fine particulate air pollution, one wouldn’t expect the pollution level on one city block to be starkly different than the pollution level on the next city block. Instead, pollution levels would smoothly taper off as one moves away from a pollution source.“For these types of problems, this spatial smoothness assumption is more appropriate. It is a better match for what is actually going on in the data,” Broderick says.When they compared their method to other common techniques, they found it was the only one that could consistently produce reliable confidence intervals for spatial analyses. In addition, their method remains reliable even when the observational data are distorted by random errors.In the future, the researchers want to apply this analysis to different types of variables and explore other applications where it could provide more reliable results.This research was funded, in part, by an MIT Social and Ethical Responsibilities of Computing (SERC) seed grant, the Office of Naval Research, Generali, Microsoft, and the National Science Foundation (NSF).

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