For what it's worth - and I don't claim to have any personal connection with it, the articles I've read on the matter describe the term "PTSD" as a broad one that encompasses many manifestations.
While some on this forum have concentrated on the stress induced by "personal danger" ala WW1 shell shock, there is a sizeable body of evidence on the effect of transgressing the intra-species killing inhibition that most successful species (homo sapiens included) are equipped with.
The figure 11 target (an identifiable human image) is used to increase the likelihood of a soldier actually aiming and firing at the enemy, by de-sensitising the intra-species killing inhibition. The same effect is achieved by letting the young play video games where humans are killed. The same effects not achieved when the target is a fictional non-human creature.
It has been proposed that the reticence that 95% of have in killing another human is increased by the proximity to the actual event. Authorising a target is likely to have less effect than using a bayonet or dagger to kill your target.
From this proposition came the argument that snipers would not be affected as much as an infantryman - but the argument was countered as snipers often see the effect of their shot in great detail. There are also inconsistencies in data as snipers are usually selected through arduous courses that play a part in their conditioning.
So where does that leave our drone operators?
Am I wrong in suggesting that they are aviators with no great driving ambition as the primary reason for career choice (as with most military aviators I know) to close with and kill an enemy?
Add to that the circumstances that allow them to identify in great detail with their target while having to conduct life as normal, as opposed to being segregated from normality and surrounded by war-going peers, and should it be any wonder that some have decided to call it a day? And what next for them? Surely leaving the job is an early symptom?
Where's the team spirit? Just because you can't see the wound, doesn't mean there isn't one. Surely the Service would be keen to show some humanity and responsibility to our front line (and they are), particularly after the MoD have been so recently criticised for the intransigence that lead to the deaths of 3 good men in training.