Over the last decade, more than a dozen Navy SEALs have taken their own lives, often displaying mysterious and uncharacteristic behaviors before their deaths. The common explanation for doctors had long been post-traumatic stress disorder. But with recent inspections of their brains postmortem, a pattern of tissue damage has been uncovered — resulting not from high-grade explosives or enemy bombardment but from repeatedly firing their own weapons. 

In his suicide note, Lt. David Metcalf described experiencing “gaps of memory, failing recognition, mood swings, headaches […] anxiety and paranoia” after serving many years as a Navy SEAL. In 2019, Metcalf collected a stack of literature about brain injuries before taking his own life. 

His brain, donated to the Department of Defense Brain Tissue Repository in Bethesda, Maryland, belongs to one of eight former SEALs who were examined for the cause of these similar symptoms after they died by suicide. All eight of them showed signs of brain damage caused by the localized blasts of personal munitions. 

Of all the wounds sustained in combat, traumatic brain injuries have appeared in recent years as the most common. Most of these cases are the direct results of a massive blast, pounding or shaking the brains in ways similar to the chronic traumatic encephalopathy that often appears in longtime football players. 

But the repeated percussion of blast waves on the brain can lead to the symptoms described by Metcalf, which were eerily similar to PTSD. They emerge gradually in ways that can be difficult to pin down. A recent Harvard University study that investigated the brains of active-duty soldiers has revealed that “high blast exposure” has been linked to thicker “cortical” tissue in the outer layer of the brain. Scanning the brains of 30 longtime Special Forces operators, scientists noted a significant warping of the brain structure in samples repeatedly exposed to shockwaves. Many soldiers experienced headaches, hallucinations, and even psychosis, reducing their memories to fragments. 

According to Dr. Daniel Daneshaber of Harvard Medical School, these blast waves can do serious damage over a long military career. 

“People may be getting injured without even realizing it,” he told the New York Times, “but over time, it can add up.” 

For years, Chief Petty Officer David Collins had been able to handle the stress and strain of five deployments to the Middle East. After 20 years in the Navy, Collins experienced severe anxiety, insomnia, and memory loss, growing baffled at simple tasks. After consulting with doctors, Collins received medication for depression and PTSD. 

“The first thing people think is, it must be PTSD, but that never made sense to me — it didn’t fit,” Collins’s wife Jennifer told the outlet. After his suicide in 2014, his brain became the first to be examined by the lab in Bethesda.

What had occurred on the microscopic level in David Collins’s brain had occurred in all eight samples. In 2016, the lab released a study outlining how these brains were affected by what is called “interface astroglial scarring.” When a soldier fires his weapon, a blast wave passes backward through the skull, rippling across the brain tissue. Further investigations have concluded that, for less than a millisecond, liquid in the back of the brain vaporizes into bubbles at a high velocity. Compared to an old party trick where smacking the top of a beer bottle can shatter its glass bottom, the shockwave will drive through the brain, reverberating back like an echo, and damage the density or stiffness of the cells.  

For years, the grieving families of SEALs like Metcalf and Collins have tried to notify military higher-ups. Whenever a SEAL is killed by his own hand, a suicide prevention course is prescribed to his company, but the link between blast damage and suicide is left out. According to the newspaper, its reporting was the first time the Navy had been notified of the connection. The lab never told its findings to the military, and SEAL leaders never did their own investigation. 

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“That’s the problem,” a SEAL leadership officer said after being notified by the media outlet. “We are trying to understand this issue, but so often, the information never reaches us.”