i was listening to a podcast a month or two ago that brought light to this problem - soldiers, who may never have seen combat but were within range of powerful blasts, can suffer enormous amounts of brain damage from it.
The episode was discussing the case of one particular soldier who worked in a support role and later went to teach a course that bombarded cadets and trainees with all sorts of simulated blasts. Just because he was there, it caused him huge amounts of brain damage only discovered after he'd killed himself.
CTE can't be reliably diagnosed right now as the only definitive test for it is to cut your brain into millimeter-thick slices and analyzing them. obviously, they can only perform this test upon the deceased.