"We looked at over 200 Special Operations Forces members who had been exposed to blasts. Even though their brains looked normal on traditional exams, we used advanced MRI to find that the ones with more blast exposure had noticeable differences in brain activity and brain structure," Dr. Diociasi said.

The service members also reported more symptoms such as anxiety, mood swings, irritability, poor concentration, forgetfulness, slowed thinking, headaches, nausea, fatigue, dizziness and balance problems, Dr. Diociasi noted.


"These symptoms were significantly more common in individuals with higher blast exposure and were linked to measurable changes in brain connectivity on advanced imaging," he said. "The more blasts someone had experienced, the more these symptoms tended to show up—and the more their brain function seemed affected."

Dr. Diociasi said that across very different populations, the same pattern emerges: mild but repetitive trauma can have lasting effects.

"We're validating and expanding on prior work using a much larger and very specific population—Special Operations Forces—while also showing that these issues likely extend beyond the military," he said. "The broader implication is that we need to rethink how we view 'mild' brain injuries, not just in soldiers, but across society."

The study challenges the idea that "invisible" injuries are harmless. Dr. Diociasi notes that many people experience multiple head impacts in their lives—whether through military service, sports, accidents or other sources. The findings show that even if these injuries don't cause obvious damage on a standard imaging exam, they can still change how the brain functions.

"We also noticed certain brain regions were actually larger in more-exposed individuals, which could reflect long-term tissue changes like scarring," he said. "These aren't injuries you can always see with the naked eye, but they are real—and now we can start measuring them."

"The findings reveal that even when the brain looks 'normal,' it might still be carrying hidden signs of trauma—and we now have tools to detect them," Dr. Diociasi said. "That opens the door for earlier detection, better treatment, and a deeper understanding of how repeated trauma affects the brain over time."

Dr. Diociasi said that with their multimodal approach, the researchers tried to connect the dots.

"But even now, many are still missing—filling in those gaps is the challenge ahead," he said.

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