Minutes after Neelix chucks Michael Jonas into a plasma fire, thus disintegrating Michael Jonas, he’s cracking jokes with Tuvok. That’s like Khan Noonien Singh levels of cold if you stop and think about it. What does that jovial exterior actually hide?
In fairness, there was a whole episode of ds9 about obrien struggling with his trauma.
Maybe their therapy techniques are as advanced as their other forms of medicine?