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.