Finalist: The New York Times, for relentless reporting by Dave Philipps

Soldiers exposed to thousands of low-level blasts from firing weapons like mortars say that they wind up with debilitating symptoms of traumatic brain injury — but no diagnosis.

By Dave Philipps

After firing about 10,000 mortar rounds during four years of training, one soldier who joined the Army with near-perfect scores on the military aptitude test was struggling to read or do basic math.

Another soldier started having unexplained fits in which his internal sense of time would suddenly come unmoored, sending everything around him whirling in fast-forward.

A third, Sgt. Michael Devaul, drove home from a day of mortar training in such a daze that he pulled into a driveway, only to realize that he was not at his house but at his parents’ house an hour away. He had no idea how he got there.

“Guys are getting destroyed,” said Sergeant Devaul, who has fired mortars in the Missouri National Guard for more than 10 years. “Heads pounding, not being able to think straight or walk straight. You go to the medic. They say you are just dehydrated, drink water.”

All three soldiers fired the 120-millimeter heavy mortar — a steel tube about the height of a man, used widely in training and combat, that unleashes enough explosive force to hurl a 31-pound bomb four miles. The heads of the soldiers who fire it are just inches from the blast.

The military says that those blasts are not powerful enough to cause brain injuries. But soldiers say that the Army is not seeing the evidence sitting in its own hospital waiting rooms.

In more than two dozen interviews, soldiers who served at different bases and in different eras said that over the course of firing thousands of mortar rounds in training, they developed symptoms that match those of traumatic brain injury, including headaches, insomnia, confusion, frayed memory, bad balance, racing hearts, paranoia, depression and random eruptions of rage or tears.

The military is confronting growing evidence that the blasts from firing weapons can cause brain injuries. So far, though, the Pentagon has identified a potential danger only in a few unusual circumstances, like firing powerful antitank weapons or an abnormally high number of artillery shells. The military still knows little about whether routine exposure to lower-strength blasts from more common weapons like mortars can cause similar injuries.

Answering that question definitively would take a large-scale study that follows hundreds of soldiers for years, and it is impossible to draw sweeping conclusions from a handful of cases. But the soldiers interviewed by The New York Times have experienced problems similar enough to suggest a disturbing pattern.

Most soldiers said they had fired at least 1,000 rounds a year in training, often in bursts of hundreds over a few days. When they were new at firing, they said, they felt no lasting effects. But with each subsequent training session, headaches, mental fogginess and nausea seemed to come on quicker and last longer. After years of firing, the soldiers experienced problems so severe that they interfered with daily life.

Nearly all of the soldiers interviewed for this article never saw combat, but they were nonetheless haunted by nightmares, anxiety, panic attacks and other symptoms usually attributed to post-traumatic stress disorder.

Nearly all sought medical help from the Army or the Department of Veterans Affairs and were screened for traumatic brain injury, but did not get a diagnosis. Instead, doctors treated individual symptoms, prescribing headache medicine, antidepressants and sleeping pills.

That is in part because of how traumatic brain injuries, known as T.B.I.s, are diagnosed. There is no imaging scan or blood test that can detect the swarms of microscopic tears that repeated blast exposure can cause in a living brain. The damage can be seen only postmortem.

So, doctors screening for T.B.I.s ask three questions: Did the patient experience an identifiable, physically traumatic event, like a roadside bomb blast or car crash? Did the patient get knocked unconscious, see stars or experience other altered state of consciousness at the time? And is the patient still experiencing symptoms?

For a T.B.I. diagnosis, the answer has to be yes to all three.

The problem is that people who are repeatedly exposed to weapons blasts often cannot pinpoint a specific traumatic event or altered state of consciousness, according to Stuart W. Hoffman, who directs brain injury research for the V.A. With career mortar soldiers, he said, “if you’re not feeling the effects at the time, but you’re being repeatedly exposed to it, it would be difficult to diagnose that condition with today’s current standards.”

That means injuries that seem obvious to soldiers go unrecorded in official records and become invisible to commanders and policymakers at the top. As a result, weapons design, training protocols and other key aspects of military readiness may fail to account for the physical limits of human brain tissue.

An Army spokesman, Lt. Col. Rob Lodewick, said in a statement that for decades the Army has been studying how to make weapons safer to fire and is “committed to understanding how brain health is affected, and to implementing evidence-based risk mitigation and treatment.”

Asked if the Army plans to phase out the use of the 120-millimeter mortar, a mobile weapon that nearly all infantry units use to rain down bombs on enemy positions, Colonel Lodewick said no.

Still, there are signs that the Army sees problems with the mortar. It is developing a cone for the muzzle to deflect blast pressure away from soldiers’ heads. And in January, the Army issued an internal safety warning, drastically limiting the number of rounds that soldiers fire in training to no more than 33 rounds a day using the weakest charge, and no more than three rounds a day using the strongest.

That warning, though, makes no mention of brain injury; the stated purpose is to protect troops’ hearing.

The military measures the force of blast waves in pounds of pressure per square inch, and the current safety guidelines say that anything below 4 PSI is safe for the brain. The blast from firing a 120-millimeter mortar officially measures at 2.5 PSI. But the guidelines do not take account of whether a soldier is exposed to a single blast or to a thousand.

There are roughly 9,000 mortar soldiers in the Army — and, in all service branches, there are thousands more troops who regularly use weapons that deliver a similar punch: artillery, rockets, tanks, heavy machine guns, even large-caliber sniper rifles.

Justin Andes, 34, launched about 10,000 mortar rounds in Army training at Fort Johnson, La., between 2018 and 2021.

He began to experience migraines, dizziness and confusion, to such a degree that his job of keeping accurate counts of weapons in his unit’s armory became a struggle. Eventually he had an emotional breakdown with thoughts of suicide, and he left the Army in dismay when his enlistment ended.

“We had to keep a count of every round we fired, and get the mortar tubes inspected each year, because all those blasts can take a toll on the weapons system,” he said in an interview. “But no one was doing that for us.”

Mr. Andes joined the Army with a college degree and top scores on the military aptitude test. He had planned to get a graduate degree in political science, but after firing so many mortar rounds, he had trouble reading. Today, Mr. Andes, who now lives in Jefferson City, Mo., speaks with a slight slur, sometimes puts the milk in the kitchen cupboard instead of the refrigerator, and spends much of his time in his basement.

“His voice is different, he acts different, he is a different person from the man I married,” his wife, Kristyn Andes, said. “I didn’t start to connect the dots that this might be mortars until some of the other wives said they were having the same issues.”

The first sergeant in charge of Mr. Andes’ platoon, she said, was having trouble, too. He was forgetting words, struggling to remember his responsibilities and had a stammer in his speech and a tremor in his hand.

Another soldier in his platoon, James Davis, 33, started having near-daily panic attacks in uniform, as well as balance problems, migraines and sensitivity to light. He went to a specialty clinic for traumatic brain injury at Fort Johnson in 2022. “I was told that with time, the symptoms would disappear,” said Mr. Davis, who now lives in Colorado Springs, in an interview. “I am still waiting for that to happen.”

Mr. Andes, Mr. Davis and their first sergeant all left the Army without any official record that their brains may have been injured by mortar blasts. All three went to the V.A. for help. All three were found to be substantially disabled by issues that can be caused by traumatic brain injury, like vertigo, headaches, anxiety and sleep apnea. But not one was diagnosed with a brain injury.

Former soldiers who fired mortars in the 1980s and 1990s say their experiences show that the problems are not new and may not improve with time.

“It’s hard for me to piece together, because my memory has gotten so bad, but things are definitely getting worse,” said Jordan Merkel, 55, who joined the Army in 1987 and fired an estimated 10,000 mortar rounds over four years.

In uniform, Mr. Merkel started experiencing strange fugue states, where he would be awake but barely responsive and would retain little memory afterward of what had happened.

After the Army, he tried college but spent most of the time struggling through remedial classes. He married and divorced three times and said that he remembers very little about those relationships.

For years he worked testing security software — a job with a predictable routine that allowed him to get by. But in 2016, he forgot how to do his work: Procedures he’d been following for years drew a blank.

He was soon laid off, got a similar job and was laid off again. He has recently noticed trouble reading an analog clock.

“I’m really concerned,” said Mr. Merkel, who now lives in Harrisburg, Pa. “This is not normal aging, this is something else.”

He went to the V.A. this spring seeking help. The medical staff asked whether he had ever hit his head or been knocked unconscious, but they seemed dismissive when he brought up mortars, he said.

“They weren’t the least bit interested in discussing anything related to blast concussion,” he said.

Todd Strader had a similar experience. He fired mortars in the 1980s and 1990s at a U.S. base in Germany, and he developed headaches so severe that he would collapse on the ground and vomit. He was hospitalized in the Army for unexplained intestinal problems — a common issue among people with traumatic brain injuries.

As a civilian, he struggled with fractured concentration, fatigue and anxiety.

“I had plans for myself after the Army,” said Mr. Strader, 54, who now lives in Apex, N.C. “I wanted to travel the world but just ended up working a string of dead-end jobs.”

He went to the V.A. in 2019 and was told that there was nothing in his record to suggest a military service-associated brain injury. Instead he was diagnosed with PTSD, even though he had never been in combat.

Frustrated that the V.A. would not recognize what seemed obvious to him, he started a Facebook group, hoping to find other mortar soldiers with the same symptoms. The group now has nearly 2,500 members.

The Pentagon has repeatedly assured Congress that the military is giving new attention to blast exposure, but ordinary soldiers say they have seen little change.

Sergeant Devaul, who drove home to the wrong house, is now trying to get the Army to recognize that years of firing mortars injured his brain. He hasn’t had much luck.

At his kitchen table in Kansas City, Mo., on a recent morning, he described how for 18 years he fired mortars, and how his life slowly fell apart.

He started in the active-duty Army in 2006 and transferred to the National Guard in 2010. He deployed twice but never saw combat.

After years of firing, he started to have trouble thinking. He had a civilian job doing carpentry but struggled with the math and organizational skills and left in frustration. He worked as a security guard for several years, but he developed headaches and concentration problems, and had outbursts of rage.

Then he got a break from firing. For much of 2017 and 2018 he was in Qatar on a mission with no mortars and then in training away from the mortar range. He began feeling clearer and calmer. He studied to become an emergency medical technician and, in 2019, got a job with his local fire department.

But that summer he resumed firing mortars. He started struggling to remember where supplies were kept in his ambulance. Other firefighters told him that he seemed to spend much of his time staring at nothing. The department asked him to learn to drive a fire truck, but he doubted that he could pass the test.

In the fall of 2021 he was firing mortars in a training exercise and suddenly felt as though a seam had split in his head. He was dizzy and sick. For weeks afterward, he said, his skull was throbbing, and he was confused and angry.

“I felt worthless and stupid,” he said. “I was so exhausted I could barely get off the couch. I didn’t see it getting better.”

His wife filed for divorce. He became suicidal and spent five days in a program for PTSD.

At his next National Guard training, it took only a few blasts to put him on the ground with the world spinning.

The Guard now lists him as temporarily disabled by what it calls “post-concussion syndrome.” He is not allowed to fire mortars or even rifles.

Since Sergeant Devaul can’t do his military job, the Guard has begun the process of discharging him. If it decides his injuries are service-related, he’ll be medically retired with lifetime benefits. If not, he’ll be forced out with next to nothing.

Sergeant Devaul met recently with his brigade’s surgeon to be evaluated for traumatic brain injury. He said the doctor seemed skeptical that firing mortars could cause his symptoms.

“I kept asking, ‘What else could have caused it?’ He didn’t have an answer,” he said. “I’ve got every single symptom of a traumatic brain injury. I just don’t have a diagnosis.”

A correction was made on May 2, 2024: An earlier version of this article included an outdated city of residence for Todd Strader. He now lives in Apex, N.C., not Hampton, Va.

A military lab found distinctive damage from repeated blast exposure in every brain it tested, but Navy SEAL leaders were kept in the dark about the pattern.

By Dave Philipps                                                                                                                             Photographs by Kenny Holston

David Metcalf’s last act in life was an attempt to send a message — that years as a Navy SEAL had left his brain so damaged that he could barely recognize himself.

He died by suicide in his garage in North Carolina in 2019, after nearly 20 years in the Navy. But just before he died, he arranged a stack of books about brain injury by his side, and taped a note to the door that read, in part, “Gaps in memory, failing recognition, mood swings, headaches, impulsiveness, fatigue, anxiety, and paranoia were not who I was, but have become who I am. Each is worsening.”

Then he shot himself in the heart, preserving his brain to be analyzed by a state-of-the-art Defense Department laboratory in Maryland.

The lab found an unusual pattern of damage seen only in people exposed repeatedly to blast waves.

The vast majority of blast exposure for Navy SEALs comes from firing their own weapons, not from enemy action. The damage pattern suggested that years of training intended to make SEALs exceptional was leaving some barely able to function.

But the message Lieutenant Metcalf sent never got through to the Navy. No one at the lab told the SEAL leadership what the analysis had found, and the leadership never asked.

It was not the first time, or the last. At least a dozen Navy SEALs have died by suicide in the last 10 years, either while in the military or shortly after leaving. A grass-roots effort by grieving families delivered eight of their brains to the lab, an investigation by The New York Times has found. And after careful analysis, researchers discovered blast damage in every single one.

It is a stunning pattern with important implications for how SEALs train and fight. But privacy guidelines at the lab and poor communication in the military bureaucracy kept the test results hidden. Five years after Lieutenant Metcalf’s death, Navy leaders still did not know.

Until The Times told the Navy of the lab’s findings about the SEALs who died by suicide, the Navy had not been informed, the service confirmed in a statement.

A Navy officer close to the SEAL leadership expressed audible shock, and then frustration, when told about the findings by The Times. “That’s the problem,” said the officer, who asked not to be named in order to discuss a sensitive topic. “We are trying to understand this issue, but so often the information never reaches us.”

The lack of communication has led Navy leaders to overlook a potentially critical threat to its elite special operators. When the commander of SEAL Team 1 died by suicide in 2022, SEAL leaders responded by ceasing nearly all operations for a day so the force could learn about suicide prevention. According to four people with knowledge of the commander’s case, his brain was later found to have extensive blast damage, but because the leaders were not told, they never discussed the threat of blast exposure with the force.

Evidence suggests that the damage may be just as widespread in SEALs who are still alive. A Harvard study, published this spring, scanned the brains of 30 career Special Operators and found an association between blast exposure and altered brain structure and compromised brain function. The more blast exposure the men had experienced, the more problems they reported with health and quality of life.

That study was funded by Special Operations Command, which has been at the forefront in the military’s effort to understand the issue. In December, the study’s main author briefed the command’s top leaders, including from the Navy SEALs.

“We have a moral obligation to protect the cognitive health and combat effectiveness of our teammates,” Rear Adm. Keith Davids, the commander of Navy Special Warfare, which includes the SEALs, said in a statement. He said the Navy is trying to limit brain injuries “by limiting blast exposure, and is actively participating in medical research designed to enhance understanding in this critical field.”

But without the data on suicides, a key piece of the problem was never discussed at the briefing.

Blows to the Head

The communication breakdown is part of a broader disconnect in the Defense Department, which spends nearly $1 billion each year on brain injury research, and many billions more to train and equip troops, but does comparatively little to ensure that the latest science on brain injury informs practices in the ranks.

Lieutenant Metcalf’s wife, Jamie Metcalf, said in an interview that she had come to see his death as an effort to draw attention to a widespread problem.

“He left an intentional message, because he knew things had to change,” she said. When told the information about his brain had not reached the SEAL leadership, she sighed and said, “You’re kidding me.”

The military readily acknowledges that traumatic brain injury is the most common injury from recent conflicts. But it is struggling to understand how many of those injuries are inflicted by the shock waves unleashed by troops’ own triggers.

There are signs that the damage can come from a wide array of weapons. Artillery crew members who fired thousands of rounds in combat came home plagued by hallucinations and psychosis. Mortar teams suffered from headaches and deteriorating memory. Reliable soldiers suddenly turned violent and murdered neighbors after years of working around the blasts from tanks and grenades in combat or in training.

Blast waves may kill brain cells without causing any immediately noticeable symptoms, according to Dr. Daniel Daneshvar, chief of brain injury rehabilitation at Harvard Medical School.

“People may be getting injured without even realizing it,” Dr. Daneshvar said. “But over time, it can add up.”

People’s brains can often compensate until injuries accumulate to a critical level, he said; then, “people kind of fall off a cliff.”

In many cases, doctors treating the injured troops give them diagnoses of psychiatric disorders that miss the underlying physical damage. Much of what is categorized as post-traumatic stress disorder may actually be caused by repeated exposure to blasts.

The stories of the SEALs who died by suicide point to a troubling pattern in the elite force.

Their average age was 43. Each had deployed to combat a number of times, but none had been wounded by enemy fire. All had spent years firing a wide arsenal of powerful weapons, jumping from airplanes, blowing open doors with explosives, diving deep underwater and learning to fight hand to hand.

Over the years they had developed the expertise and sharp judgment of seasoned special operators. But late in their careers, the effects of years of repeated blast exposure ate those skills away.

Around the age of 40, nearly all of them started to struggle with insomnia and headaches, memory and coordination problems, depression, confusion and, sometimes, rage.

“The first thing people think is, it must be PTSD, but that never made sense to me — it didn’t fit,” said Jennifer Collins, whose husband, retired Chief Petty Officer David Collins, was a SEAL for 20 years and died in 2014, just over a year after leaving the Navy.

A Late-Career Breakdown

Ms. Collins is the reason that the brains of a high proportion of the SEALs who died by suicide made it to the Defense Department’s lab.

Her husband was in many ways a typical SEAL: smart, confident, easygoing and high-achieving. He deployed to Afghanistan twice and to Iraq three times. When he was not deployed, he was away from home for hundreds of days each year in training.

Combat never seemed to faze Mr. Collins, but near the end of his Navy career, he started to change in subtle ways that Ms. Collins pieced together only in retrospect. He began to avoid social gatherings. He struggled to sleep. He started to make strange, obsessive family schedules and become irritated when they were not followed. Some simple chores, like raking leaves into a tarp, started to confound him. He would step out the door to go to work, realize that he had forgotten his keys, go back inside to get them and then forget why he had returned.

All were signs of brain injury. But at the time, the military generally associated brain injury with big blasts from roadside bombs — something Mr. Collins never experienced. No one was telling the troops that repeated exposure to routine blasts from their own weapons might be a risk.

Mr. Collins’s mental health took a sudden plunge when he was 45. He had left the Navy and started a civilian job teaching troops to operate small drones. One morning, well before the sun was up, he called his wife in a panic from a work trip, saying he had forgotten how to do his job and had not slept in four days.

“He was super anxious, almost paranoid,” Ms. Collins recalled. “He was nothing like my husband.”

When Mr. Collins returned to the couple’s home in Virginia Beach, doctors scanned his brain with magnetic resonance imaging but found nothing abnormal. They eventually gave him a diagnosis of depression, anxiety and post-traumatic stress disorder, and prescribed a number of drugs for sleep and mood. They didn’t help.

He then went to a specialty clinic for brain injury but failed to find relief.

Everyday tasks like booking a flight became so arduous that he would puzzle over them for hours. He was sleepless and agitated — scared that his mind was slipping away.

In March 2014, three months after placing the frantic pre-dawn call to his wife, he went to return a few library books, dropped off a tuition check at his son’s kindergarten, and then drove to a secluded side street. He sent a text to his wife saying, “So sorry, baby. I love you all,” and ended his life.

“I knew, with all he had been going through, that the text could only mean one thing,” Ms. Collins said.

When the police came to the house to confirm his death, she was adrift in grief and confusion. But one determined thought floated to the front of her mind.

“I told the police — I was adamant — that I wanted his brain donated to research,” she recalled. “I wanted to try to find some answers.”

Visible Under a Microscope

In Bethesda, Md., the Defense Department had built a lab in 2012 called the Department of Defense Brain Tissue Repository, whose goal was to gather the brains of deceased veterans to look for clues to the two most widespread injuries of recent wars, PTSD and traumatic brain injury. But two years after opening, the lab faced a fundamental problem: It had no brains to study.

The lab depended on tissue donations from the families of war veterans who had recently died, but few families knew it existed, and the lab’s bylaws barred it from cold-calling grieving families to ask. Brain tissue deteriorates quickly; by the time most families found out about the lab, it was too late.

Ms. Collins’s quick decision meant that her husband’s brain was soon packed in ice and on its way.

That single brain revealed a pattern of damage that the head of the lab, Dr. Daniel Perl, who had spent a career studying neuropathology in civilians, had never seen before. Nearly everywhere that tissues of different density or stiffness met, there was a border of scar tissue — a shoreline of damage that seemed to have been caused by the repeated crash of blast waves.

It was not chronic traumatic encephalopathy, or C.T.E., which is found in football players and other athletes who have been repeatedly hit in the head. It was something new.

The lab’s research team started looking for similar damage in other brains. In civilians’ brains, they did not find it. Nor was it in the brains of veterans who had been exposed to a single powerful explosion like a roadside bomb. But in veterans exposed repeatedly to blasts, they found it again and again.

The team published a landmark study in 2016 reporting the pattern of microscopic damage, which they called interface astroglial scarring.

“For the first time, we could actually see the injury,” Dr. Perl said in an interview. “If you know what the problem is, you can start to design solutions.”

Dr. Perl said privacy rules bar him from discussing specific cases, but members of the families who provided brains to study say the lab found interface astroglial scarring in six of the eight SEALs who died by suicide. The other two SEALs, including Lieutenant Metcalf, had a different type of damage in the same blast-affected areas. Star-shaped helper cells called astrocytes in their brains appeared to have been repeatedly injured and had grown into gargantuan, tangled masses that barely functioned. The lab plans to publish findings on the astrocyte injuries soon.

Recent studies suggest that damage is caused when energy waves surging through the brain bounce off tissue boundaries like an echo, and for a few fractions of a millisecond, create a vacuum that causes nearby liquid in the brain to explode into bubbles of vapor. Those tiny explosions are violent enough to blow brain cells apart in a process known as cavitation.

Dr. Perl shared with Ms. Collins what he had found in her husband’s brain in 2016, and she made it her mission to get more families to donate.

Spreading the Word

For the next several years, Ms. Collins told anyone who would listen about his case — Navy SEAL leaders, veterans’ groups, gatherings of wives. And when a career SEAL died by suicide, a call from Ms. Collins often soon followed. In 2017, she called the parents of Special Operator First Class Ryan Larkin. A few months later, she sat down with the wife of retired Chief Petty Officer Bill Mulder.

“She had the paperwork in her hand, and said, ‘I think this would be a smart thing to do,’” Mr. Mulder’s wife, Sydney Mulder, recalled in an interview. “I was in a blur, but I didn’t hesitate, and I’m glad I did it.”

Ms. Collins’s influence spread until brain donation became somewhat common for Special Operations troops. But little of what the researchers have learned from those brains made it back to the SEAL team leadership.

Mr. Mulder, like Mr. Collins, had spent a career in the SEALs but had never been wounded. He was an explosives expert in the elite SEAL Team 6, exposed to thousands of blasts in training.

After years of steady service, he went into a steep decline. He couldn’t sleep and was constantly misplacing things. Frustration would send him into a rage. He stewed over negative interactions in his squadron and started drinking before work.

“For all the years I’d known him, he had been such a capable man,” Ms. Mulder said. “He would wake up at six in the morning and get his workout. He was incredibly smart and organized and diligent. And then he just wasn’t.”

After years of trying to get help from doctors who largely overlooked the possibility of brain injury, Mr. Mulder took his own life at age 46.

Jamie Metcalf also noticed a sudden decline in her husband when he returned in 2018 from his fifth deployment. For years, Lieutenant Metcalf had been a high achiever. He was an enlisted SEAL sniper, and taught martial arts to other SEALs. A few years before he died, he decided to pursue a military medical career, became an officer and sailed through the demanding training program for physician assistants.

But after his final deployment, he was moody, confused and plagued by headaches. He put wet laundry in the dryer on top of dry clothes. One day he emptied out the kitchen cupboards to organize them, then left everything in piles on the counter.

“It was so unlike him — he had always been so organized,” Ms. Metcalf said. “Now I know he was afraid there was something happening in his brain, but at the time, I think he tried to hide it.”

He died a few months later at age 42.

The men who died by suicide represent only a small fraction of the career SEALs with signs of brain injuries after years around blasts.

Several SEAL veterans said in interviews that many of their former teammates are now divorced and grappling with depression, paranoia and substance abuse — all of which can be caused by deteriorating brain function. Desperate calls from suicidal friends are common, they said.

Ms. Metcalf saw how broad the problem was when she read the letter her husband had left about his brain injury symptoms to two of his SEAL friends.

“One of them was crying on my lap, saying, ‘That’s me, that’s me,’” she said. “And the other told me a lot of them have problems, but don’t know what to do.”

If you are having thoughts of suicide, call or text 988 to reach the 988 Suicide and Crisis Lifeline or go to SpeakingOfSuicide.com/resources for a list of additional resources.

The pounding that sailors’ brains take from years of high-speed wave-slamming in the Special Boat Teams can cause symptoms that wreck their careers — and their lives.

By Dave Philipps

In the year before Troy Norrell died, he grew convinced that the government had somehow infiltrated his brain. And in a way, he was right.

The 44-year-old was a rising star in the Navy’s Special Boat Teams — an elite group of stealth speedboat crews who can race over rough seas at 60 miles an hour to deliver Navy SEALs to their targets. But after years of pounding across the waves, he was barely able to function. He grew forgetful and confused. He struggled with insomnia, alcohol abuse and rage. On a training trip, he smashed a rearview mirror and started cutting his chest with the glass.

He was forced to medically retire in 2017 after 12 years in uniform.

As a civilian, he grew delusional and paranoid, and started to believe that the government had bugged his phone, then his kitchen walls and finally his own skull.

“There’s only a little piece of me left,” he told a neighbor in 2021, tapping his head. “They got the rest.”

A few days later, he was found dead of a self-inflicted gunshot wound in a field near his home in the San Diego suburbs.

An autopsy revealed that his brain was riddled with chronic traumatic encephalopathy, or C.T.E., a progressive disease often associated with football players who suffer repeated blows to the head.

A Defense Department neurologist who analyzed samples of Mr. Norrell’s brain wrote that his C.T.E. probably came from years of impacts with waves. The neurologist alerted the Navy that other sailors in the Special Boat Teams might face the same risk.

As if to underline the point, six weeks after Mr. Norrell’s death, another boat team member in the grip of paranoid delusions, Travis Carter, 33, died by suicide a few miles away.

Seeking an edge in combat, the Navy has created boats so powerful that riding in them can destroy sailors’ brains, several former senior members of the Special Boat Teams said.

In interviews, 12 former boat team leaders — nearly all chiefs or senior chiefs — said the damage piles up almost unnoticed for years, and then cascades, often around the time sailors move into leadership roles. Rock-solid sailors like Mr. Norrell become erratic, impulsive and violent. Many develop alcohol problems, get arrested for bar fights or domestic violence, or become suicidal. One was charged with threatening to kill President Barack Obama.

“Over and over and over, high-performing guys spiral down and fall apart,” said Robert Fredrich, 44, a retired senior chief who served in the teams from 2001 to 2023. “It happened to me, it happened to most of my friends. When it does, they kick us out or force us to retire, but never address the real issue.”

Every boat crew veteran interviewed by The New York Times recalled seeing the pattern play out repeatedly.

It is unclear how many sailors have been injured. There is no public data from the Navy, and even if there were, no blood test or brain scan exists that can definitively detect in a living sailor the type of damage that an autopsy found in Mr. Norrell.

In a questionnaire sent to boat team veterans by one retired chief, nearly all who replied — about 300 — said they had experienced concussion symptoms from riding on the boats, and most were still experiencing symptoms years later. Nearly a quarter said they had been suicidal.

The widespread reports of injuries point to a problem with implications that go beyond one small, specialized Navy unit: In its push for ever more powerful equipment, the military may have exceeded what many human brains can handle.

The Pentagon has started to acknowledge that repeatedly firing weapons like howitzers and rocket launchers may cause serious injuries to troops’ brains. But the experience of the Special Boat Teams suggests that the problem may extend beyond blast exposure to include getting jolted and knocked about in high-performance vehicles.

In other parts of the military, post-traumatic stress disorder from combat is often seen as a driving factor when top performers fall apart. In the boat teams, though, few sailors ever see combat. Not knowing what else could be behind the epidemic of behavioral issues, veterans said, leaders have repeatedly blamed the sailors themselves.

In interviews, a number of former senior chiefs said that at the point when they were promoted to positions overseeing critical missions, they were already stumbling over words, losing their trains of thought, and getting distracted by family lives that were falling apart.

“The problem is, we have dudes with brain injuries leading dudes with brain injuries, and they are unable to fully comprehend what is going on,” Mr. Fredrich said.

The Navy and the Defense Department have been tight-lipped about what they know. The Defense Department brain lab that found C.T.E. in Mr. Norrell refused to say how many boat team members’ brains it has examined, or what it has found in them. More than 70 current and former boat crew members have participated in a brain injury study at Tulane University, but the Navy and Tulane each declined to describe the findings.

A spokeswoman for Naval Special Warfare, which oversees the boat teams, said in a written response to questions that the risks to the boat crews “are well recognized,” but would not address whether those risks include brain damage.

The spokeswoman disputed that leaders may be particularly affected, noting that they undergo extensive testing and are chosen for their “sustained superior performance.”

In 2021, medical staff members at Naval Special Warfare started slipping a memorandum into crewmen’s files, warning future medical providers that the crews were “subject to large shock and vibration forces,” and that their heads experienced sudden jerks of up to 64 Gs (64 times the force of gravity). Fighter pilots typically experience a maximum of about nine Gs.

The medical memorandum suggests that some in the Navy are concerned about the risk of brain damage. The Navy has made changes in recent years to improve detection and treatment of brain injuries.

But veterans say operations have continued unchanged, and any lessons from the suicide deaths seem to have been missed.

“No one was asking, ‘What the hell is going on here?’” said Mr. Fredrich, who was still in the teams when Mr. Norrell and Mr. Carter died. “It was just, ‘Well, what a tragedy. Now get back in the boats.’”

The Special Boat Teams were established in the late 1980s to speed Navy SEALs to their targets. The Navy had been using small patrol boats since World War II, but those boats topped out at about 30 miles an hour, and the crews serving on them usually stayed only a few years before moving to other assignments. The new teams acquired high-powered racing boats and trained a new class of career operators known as Special Warfare Combatant-Craft Crewmen, or SWCCs, who stayed for their entire careers.

Several former crewmen said skipping over big waves and hitting the faces of the next ones was like being in repeated car crashes.

“The first hit weakens you, and you are still trying to recover when the next one hits,” said Steve Chance, who served in the first generation of boats in the 1990s. “You do that for hours, and it feels like someone worked you over with a pool cue. Sometimes you’d slam so hard you’d have a headache for a week.”

Almost immediately, crews started reporting high injury rates. In 1994, a Navy study put sensors on boats and found that crews experienced more than 120 whiplash events per hour. The force of the hits, the study said, was “a challenge to human tolerances.”

The Navy added better shock absorbers to the seats of some boats in the 2000s, but former sailors said the boats hit the waves with such force that those seats often broke.

“It was so violent,” said Anthony Smith, who joined the boat teams in 1996 and rose to the rank of chief. “You couldn’t think straight, your back hurt, your neck hurt, and all the guys would have blood in their urine.”

Repeated jolts to the head can fray neurons over time, leading to impulsive decisions, violent reactions, depression and psychosis. Sailors often saw the battering as part of the job and endured it without complaint, unaware of the long-term consequences.

After eight years on boats, Mr. Smith developed an overwhelming sensation that he was existing outside his own body. He had crippling depression and panic attacks. In 2004, he had a seizure with convulsions so strong that his shoulder dislocated. Like many others, he was quietly retired from the Navy on medical grounds.

“No one in the Navy ever said the words ‘brain injury,’” he said. “The psychologist told me I was depressed because I didn’t want to leave the Navy.”

Determined to learn whether others were having similar troubles, Mr. Smith recently started sending questionnaires and found nearly all were reporting issues.

The Navy introduced a new generation of boats about a decade ago, in part to try to smooth the ride, but sailors say the improved technology just allowed crews to go faster, and the slamming continued.

One new model was the 2,500-horsepower, $11 million Combatant Craft Medium, and one of the first sailors to man it was Travis Carter, who died by suicide in 2021. Sailors said the boat performed well, but the pounding across the waves continued at faster speeds.

“We all got destroyed,” said Mr. Fredrich, the retired senior chief, who worked with Mr. Carter.

Mr. Carter’s memory started to crumble and his moods swung so violently that his wife thought he was bipolar. He was racked by delusions and would boil with rage, smash things in his house and then act as if nothing had happened.

“He was two completely different people, and he was getting violent to the point where it was scary,” his widow, Nichole Carter, said in an interview.

The boat teams pulled Mr. Carter from a leadership position in 2021 because of his strange behavior. Though the military has a world-class brain injury clinic only a few miles from his base near San Diego, the boat teams didn’t send him there because he was about to deploy for a fourth time. He died five days before he was due to leave.

“He knew there was something really, really wrong, but the Navy said they were going to deal with it when he got back,” Ms. Carter said.

The medical examiner in San Diego sent Mr. Carter’s brain to the Defense Department brain lab in 2021. This October, his family finally got a letter about the results. The letter was clear on what the lab had not found — no C.T.E., it said — but it was vague about whether the lab had found other damage.

All the boat crew veterans interviewed by The Times said they repeatedly saw squared-away sailors like Mr. Carter unravel as they climbed in rank. Chiefs who once seemed flawless went blank during briefings, wrecked boats or landed in jail.

“It is far too common to be a coincidence,” said Kyle Zellhoefer, who served for 20 years in the Navy. “I’ve seen it happen over and over. It happened to me.”

By the time Mr. Zellhoefer reached the rank of chief in 2017, he was having headaches so debilitating that his vision would blur and he was screaming at people, just as he had seen chiefs before him do. A shoving match with a master chief in 2019 led to formal punishment and stalled his career. He transferred out of the boat teams, and then retired from the Navy over the summer.

“It probably saved my life to get pushed out when I did,” he said. “I’ve seen how others have ended up.”

If you are having thoughts of suicide, call or text 988 to reach the 988 Suicide and Crisis Lifeline or go to SpeakingOfSuicide.com/resources for a list of additional resources. Go here for resources outside the United States.

A confidential Navy program is studying whether intense fighter jet operations can cause devastating brain injuries in flight crews.

By Dave Philipps

To produce the best of the best, the Navy’s elite TOPGUN flying school puts fighter pilots through a crucible of intense, aerial dogfighting maneuvers under crushing G forces. But behind the high-speed Hollywood heroics that the school is famous for, the Navy has grown concerned that the extreme flying may also be producing something else: brain injuries.

This fall, the Navy quietly began a confidential project, code-named Project Odin’s Eye, to try to find out. The effort will collect roughly 1,500 data points on brain function for each TOPGUN pilot who flies the Navy’s workhorse fighter jet, the F/A-18 Super Hornet, according to communications by the project’s staff. The goal is to understand the scope of the problem and identify pilots who are injured, the communications said.

Some pilots say the effort is long overdue. In interviews, more than a dozen current and former Navy fighter-crew members said that years of catapult launches from aircraft carriers and body-crushing, high-speed maneuvers can take a cumulative toll. At the end of their careers, they said, some top performers become confused, erratic and consumed by anxiety and depression.

Pilots said the symptoms are routinely dismissed as unrelated mental health problems. In addition, they said, pilots often hide symptoms in order to keep flying.

Some eventually fall into a tailspin. In the past 18 months, three experienced Super Hornet pilots have died by suicide. According to their families, all had symptoms consistent with brain injuries.

Officially, the Navy denies that there is a problem. In a statement to The New York Times, a Navy medical spokesman said the Navy “has no data or research to prove any relationship between concussive injuries and either carrier takeoffs/landings or routine combat maneuvers.”

Even so, for years the Navy has quietly sent pilots to civilian brain injury clinics and has funded research suggesting that the conditions crews experience in jet cockpits could cause brain injuries.

Project Odin’s Eye was created earlier this year to look for brain injuries in Navy SEALs. It expanded in November to include TOPGUN aviators, according to project communications viewed by The Times. To quickly address a pressing need, the project began without formal approval from Navy Medical and Air Commands, according to a Navy official, who asked not to be named in order to discuss the confidential program. Higher Navy command may not yet be aware of it, the official said.

A Navy Special Warfare spokeswoman confirmed the existence of the program.

For years, the Navy has studied how much force a pilot can tolerate in one flight, and generally maintained that brain injuries happen only when something goes wrong. But it has paid little attention to the cumulative effects of the hundreds of flights that occur within a career, and evidence has been mounting across the military that repeated exposure to routine operations can damage brain cells even if the operations go right.

Most of the concern has focused on ground troops, like artillery and mortar crews, grenade instructors and Navy SEALs, who are frequently exposed to blast waves. If fighter crews face the same risk, it could have vast implications because of the Navy’s huge investments in aircraft carriers and high-performance jets.

The name Odin’s Eye refers to a Norse legend about a god who sacrifices an eye to gain knowledge. Whether the project will find widespread injuries in pilots’ brains is far from clear. Still, the fact that the Navy is now investigating shows that it is concerned about the risk.

“No one is talking about it, but this is a big problem,” said Dr. Kristin Barnes, who flew in a precursor to the Super Hornet, the F-14 Tomcat, as a radar intercept officer for 22 years and then became a doctor. “When you launch from the carrier, you accelerate from zero to almost 200 miles per hour in two seconds, and your brain gets squished to the back of your skull. You can heal from that once — you can heal from it 10 times. But I did it 750 times.”

The human brain has a consistency similar to that of Jell-O, and it holds 100 billion neurons connected by biological wires so delicate that 150 of them could fit within a single human hair. Enough force whipping through the brain can cause those connections to tear.

The brain can compensate, sometimes for years, by rerouting signals through healthy connections. But doctors and scientists who have studied repetitive head injuries say the damage can build up, and if enough routes become blocked, normal functions veer off course.

A decade into her career, Dr. Barnes started wondering why she was having so many problems. She had grown sensitive to noise and light, and developed vertigo and heart palpitations — all potential symptoms of brain injury.

By the time she retired in 2015, she was spacing out at work and forgetting entire conversations. She had always been a top student, but nearly flunked out of medical school. It was years later that a civilian doctor told her she probably had a brain injury.

“For a long time, I thought I was the problem,” said Dr. Barnes, 55. “It never occurred to me that flying could do this to me.”

In aerial dogfighting, a jet veers and dives at more than 500 miles an hour, sending brain tissue on an extreme roller coaster ride that may tear connections between cells, several neurologists said. At the same time, the force of the turns drains blood from the head, potentially starving the brain of oxygen.

“Those turns look graceful from the ground, but inside the cockpit you are vibrating like crazy and fighting to stay conscious,” said Mark Keller, who flew in the back seats of Navy fighters as a weapons officer from 1996 to 2012.

In extreme cases, crew members can black out. But even in routine training maneuvers, he said, crews often “gray out” by flying so close to the limit that their vision fades to a narrow, colorless tunnel.

“Obviously, that’s not good for you,” Mr. Keller said. “And I think it might explain a lot about what happened to me.”

By the end of his Navy career, Mr. Keller, once happy and easygoing, was getting into fistfights with fellow officers. After the military, he started smoking marijuana to cope with crippling anxiety and depression, and then began injecting cocaine.

“My whole personality changed,” he said. “I was completely unregulated and unable to make good decisions.”

Fighter pilots said they received little safety education concerning brain injuries. Many are unaware of the potential causes or symptoms. Mr. Keller sought treatment for depression and addiction, but never thought to ask about a brain injury.

There are few publicly available studies on the neurological effects of flying fighter jets. Two of the most recent each found that pilots had decreased brain function compared with control groups.

Those findings match what some doctors who specialize in brain injuries say they have seen in pilots.

Russell Gore was an Air Force flight surgeon before becoming a civilian neurologist. In 2019 the Navy sent him a half-dozen fighter pilots who were experiencing issues with memory, clouded thinking and anxiety. To him, they resembled veterans he had treated who had been repeatedly exposed to blasts. He took his concerns to the Navy in 2020.

A doctor at the Department of Veterans Affairs who treated several pilots in 2021 reached a similar conclusion.

In a statement, the Navy said that factors other than flying may cause brain injuries in pilots and that “no blanket conclusions can be drawn.”

The lack of awareness of brain injury risks in fighter squadrons may have allowed a number of pilots to fall apart without proper help.

Capt. Jake Rosales was a hotshot among hotshots. He aced TOPGUN, became one of its leading instructors and made the toughest dogfighting moves look easy.

“He was almost the perfect pilot,” said Jeff Fellows, who was a fellow instructor. “He could fly the jet to the very edge of the envelope.”

By the end of his career, though, after 23 years of catapult takeoffs and skull-shaking turns, Captain Rosales grew forgetful and depressed. The Navy had trained him to make quick, clear decisions, but he became so consumed by anxiety that even simple choices sometimes seemed impossible.

One night in 2020, he went to the market to buy cheese for a family taco night, but he called his girlfriend upset because he was unable to decide which of the store’s three shredded Mexican blends to buy.

“He was completely fraught,” his girlfriend, Ann-Marie Avanni, recalled in an interview. “The anxiety could be paralyzing.”

Unaware that he might have a brain injury, he began to see himself as a failure. In the summer of 2023, he died by suicide, alone on a beach near San Diego.

At first, his death was widely seen as a tragic outlier. But then a second pilot died by suicide in January 2024. And then a third in March. All three were in their 40s; they all flew the Super Hornet.

After the deaths, the Navy scrambled to ramp up mental health resources in fighter squadrons, but missed a rare opportunity to understand the physical side of the problem.

There is no available test that can definitively detect the microscopic damage caused by repeated sub-concussive injuries in a living brain. They can only be diagnosed postmortem by a few specialized laboratories.

The Defense Department has such a lab, but no one thought to send Captain Rosales’s brain tissue to be tested after he died, his friends and family said.

Those close to Captain Rosales describe a decline that neurologists say is consistent with brain injury.

He started flying Super Hornets in 2003 and was chosen in 2007 to attend TOPGUN. For three years, first as a student and then as an instructor, he flew high G-force maneuvers nearly every day — sometimes twice a day.

By the time he was promoted to captain in 2021, he had flown 3,281 hours and made more than 400 carrier landings. But years of hard flying were changing him. He developed headaches and panic attacks, mood swings and severe memory lapses.

Lisanne Rosales, his wife at the time, said she urged her husband to seek counseling, but Navy regulations can restrict pilots with a diagnosed mental health condition from flying. If he disclosed his issues, she recalled him telling her, the Navy would ground him, effectively ending his career.

The couple lived apart for several years, and divorced in 2021.

“I think the Navy failed him,” Ms. Rosales said. “He didn’t feel he could talk about his mental health issues, so he white-knuckled them in silence.”

Several other pilots said in interviews that they, too, hid symptoms, and continued to do so in civilian life because of similar restrictions for commercial pilots.

Two men who flew with him were secretly struggling with similar problems.

Scott Walters was a fellow TOPGUN instructor who flew in Captain Rosales’s back seat. Halfway through his career, he started having episodes where his heart felt as though it would beat out of his chest. He became depressed, started drinking before work, became suicidal and was eventually forced to retire.

“I was really, really out of control,” he said. “I couldn’t figure out what was wrong with me.”

Ian Gorski also flew in the captain’s back seat. He developed unexplained anxiety attacks that made him vomit before work, and his thoughts began to skip around half-finished, he said, “as if I had 20 squirrels running around my brain.”

He sought counseling after leaving the Navy, but said he never considered that he might have a brain injury. When told recently about Captain Rosales’s struggle in the supermarket, Mr. Gorski started to cry.

“There is no way the man I flew with couldn’t pick out cheese,” he said. “He was almost a god. No one was better. It makes no sense.”

Then, after a long pause, he added: “But I’m having a lot of the same issues. A lot of us are.”

f you are having thoughts of suicide, call or text 988 to reach the 988 Suicide and Crisis Lifeline or go to SpeakingOfSuicide.com/resources for a list of additional resources. Go here for resources outside the United States.

A correction was made on Dec. 8, 2024: Because of an editing error, an earlier version of this article referred incorrectly to Dr. Kristin Barnes’s career as an aviator in the Navy. She was a radar intercept officer who flew in fighter jets; she was not a pilot.

A correction was made on Dec. 13, 2024: An earlier version of this article, and an accompanying picture caption, misspelled the given name of the woman who was Jake Rosales’s girlfriend at the time of his death. She is Ann-Marie Avanni, not Anne-Marie.

A military report on suicide rates broken down by occupation finds the highest rates among categories of troops that often work and train around weapons blasts.

By Dave Philipps

Troops whose jobs can expose them repeatedly to blasts have among the highest suicide rates in the armed forces, according to a new report by the Defense Department.

The report, released on Wednesday, lists the suicide rates for each military occupational specialty between 2011 and 2022.

Explosive ordnance disposal team members, who disable roadside bombs and routinely train and work around very large blasts, had the highest suicide rate — 34.77 deaths per 100,000 people per year — followed by infantry and special operations forces; armor crews; and artillery troops; whose rates are closer to 30 deaths per 100,000.

The rates for these combat occupations are roughly twice those of service members who work in noncombat jobs like data processing or food service.

The current national rate for civilians is about 14 deaths per 100,000 per year.

The report released on Wednesday does not mention blast exposure as a factor, and offers no insights into what may be contributing to the different suicide rates. Still, the correlation between deaths by suicide and levels of blast exposure is a common theme in the figures.

Defense Department studies suggest that most blast exposure happens in training, not combat.

In the Air Force, where blast exposure is rare, there were no significant differences in suicide rates among different military occupations. But among Army and Marine Corps troops, the rates are elevated wherever blasts are part of daily work.

“This comes as no surprise,” said Chuck Stansberry, a recently retired Navy master chief who worked in explosive ordnance disposal for most of his career. “I can’t tell you how many guys I know who have died of suicide.”

Troops in his career field train around blasts on almost a weekly basis, and can be exposed to blasts of 1,000 pounds, he said. While they are required by safety guidelines to keep their distance to avoid having their eardrums blown out, the guidelines take no account of blast exposure risk to their brains.

Blast exposure has long been a misunderstood hazard, Mr. Stansberry said, adding that by the end of his career, he was grappling with sleeplessness, depression and severe memory problems.

“A lot of us are like that,” he said. “It’s not psychological — there is something physiologically wrong. And a lot of guys struggle.”

The report said that 5,997 service members died by suicide between 2011 and 2022 — more than six times the number killed in combat during the same period.

Eight Navy SEALs who died by suicide in the last 10 years, and whose brains were then studied in a specialized laboratory, all showed characteristic signs of damage caused by repeated blast exposure, an investigation by The New York Times found.

The overall suicide rate in the military has been increasing for 20 years. The stresses of war were long thought to be a driving factor in the increase, but the trend has continued even as the combat tempo has ebbed over the last decade, leaving many military leaders perplexed.

For years, the military has taken a one-size-fits-all approach to suicide prevention, stressing education of troops about the signs of suicide risk and the availability of mental health care. It has done comparatively little to pinpoint upstream causes.

The Defense Department report was initiated by Senator Angus King of Maine, who released the findings on Wednesday. In a statement, Mr. King said he hoped the data would guide the military “in its efforts to curb suicide rates and hopefully save lives.”

Legislation introduced by Mr. King that is pending in Congress would require the military to start releasing data on suicide by career field each year.

Mr. King and 10 other senators sent a letter in May to Congressional leaders expressing their concern that shock waves from weapons blasts may be causing brain injuries that go unrecognized by the military. “We need to better understand the potential physical, cognitive and behavioral impacts that exposure to these shock waves can have on service members,” the letter said.

Suicide is complex and rarely hinges on a single factor, but a number of studies, including some funded by the Defense Department, have shown that traumatic brain injuries can increase the risk.

Blast waves surging repeatedly through the brain can destroy cells, fray connections and lead to a tangle of mental health problems that are often not recognized as being caused by brain injury, including nightmares, insomnia, depression, anxiety, substance abuse and social isolation. Many service members who receive diagnoses of post-traumatic stress disorder may actually have brain injuries that produce similar symptoms, scientists say.

Even so, for decades the military largely overlooked the risk to brain health posed by the blast waves from weapons fired during training. Only in the last few years, when forced by Congress, has the military taken action on the issue.

The new report shows heightened suicide rates in some military occupations that are not obviously exposed to blasts, like medical care providers and radio operators. However, troops in those occupations — including combat medics — are sometimes embedded in combat units, where they may be exposed to many of the same stresses and blast waves as combat troops, even though they are counted separately in the report.

Because the report does not break out data on individual specialties within each broad career field, troops who may be at very high risk, like mortar teams, may be lost in the figures for the larger categories to which they belong, like infantry.

Risk factors other than blast exposure may be contributing to higher suicide rates, said Katherine Kuzminski, an expert on the military and veterans at The Center for a New American Security. For example, bomb technicians may deploy more often, and be exposed to more traumatic situations, than other troops, she said. And high-risk combat jobs may attract people with pasts that predispose them to suicide risk, independent of what happens while they are in uniform.

“This report is a good first step,” Ms. Kuzminski said. “It provides us the data to start asking the right questions. But there are still a lot of questions.”

Chief among them, she said, is how exposure to repeated blasts from weapons affects suicide risk.

The military does not track the blast exposure of individual service members, so it does not have data to show whether exposure erodes mental health.

Wearable blast sensors have been available for more than a decade, and have sometimes been employed by the military in field research. Thousands of soldiers wore them in Afghanistan as part of a study of brain injuries from roadside bombs and enemy attacks. The data revealed that a vast majority of blasts that the troops were exposed to came not from enemy action but from soldiers’ own weapons. The research program was shelved a short time later.

Special Operations Command, which oversees Army Green Berets and Navy SEALs, among others, is in the final stages of issuing wearable blast gauges to all its operators. Congress recently required the rest of the military to begin tracking blast exposure in all other troops, but the military is considering using computer modeling to assign doses to troops, instead of issuing millions of individual gauges.

Congress’s interest in the issue has been heightened recently by the revelation this spring that Robert R. Card II, an Army Reserve soldier who went on a deadly shooting rampage in October, killing 18 people and himself in Lewiston, Maine, was found by a Boston University laboratory to have had extensive brain injuries that were probably caused by blast exposure.

Mr. Card’s case shows the limitations of analyzing risk of blast exposure through a soldier’s career field. To the Army, Mr. Card was officially a petroleum supply specialist — an occupation not at all associated with weapons blasts. But despite that career designation, he worked for years as a grenade instructor, where his brain was exposed to blasts by the thousands.

Army investigators said in a recent report that they saw no link between Mr. Card’s service in the Army Reserve and his deteriorating mental health.

If you are having thoughts of suicide, call or text 988 to reach the 988 Suicide and Crisis Lifeline or go to SpeakingOfSuicide.com/resources for a list of additional resources.