Pentagon Data Shows High Suicide Rates Among Troops Exposed to Blasts

The paragraph before the one you quoted says it:

Explosives ordinance 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.

That's a 15% bump in suicide for the most blast exposed troops when compared to less blast exposed combat troops.

Obviously combat exposure vs not is going to have a large effect, but blast exposure seems to have a further effect on top the horrors of combat.

Also:

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

The report presented the data, but made no attempt to grapple with the implications:

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

It's a gift link, so you shouldn't hit the paywall if you've got javascript enabled and aren't running a browser extension which strips off the gift token.

TL;DR; It's due to brain damage.