Looking at a special function requiring specific training and high percentage of dismiss /reject is a little skewed for such study between well-being after deployment.
I will not be surprised if NCO and specialists resilience to stress fight is the same as snipers.

It could be interesting to find out that nature of character (psychological orientations) are less fight-stress relevant.

Last point, 19 is not a big enough sample from a statistical point of view. Furthermore, the candidates were chosen by their staff, polluting the sample.