Post-Traumatic Stress Disorder - Tolkien and his Characters

[Pitchwife]

I'd agree with Bêthberry that Celebrían's an obvious example - she passed into the West in the year after her traumatic experience, so obviously she couldn't bear to live with it any longer.
Another character who came to my mind in this context is Gwindor of Nargothrond from the Silmarillion. His life-story is one of the most poignant in the whole Legendarium. First he has to watch his brother being maimed and hacked to pieces by the Orcs at the beginning of the Nirnaeth. Then, when he allows himself to be provoked into leading a premature charge by this atrocious act, he is captured alive and dragged to Angband to endure sixteen years of slavery as Morgoth's thrall - an experience from which he never recovered.
When Beleg found him after his escape, he was but a bent and fearful shadow of his former shape and mood, and his own people in Nargothrond didn't recognize him, because he looked like one of the aged among mortal Men (sorry, no literal quote - I'm re-translating from my German version of the Silm). What does it take to make an immortal Elf look like that? I'm certain the damage done to him was more than merely skin-deep. Actually, now I think about him a little closer, I picture him like the Middle-Earth equivalent of a survivor from Auschwitz, and I'm pretty sure he awoke screaming from nightmares of Angband every other night during the rest of his life.
And as if all that was not enough, he had to watch Túrin ruining his home, his love and whatever else remained of his former life that was precious to him. Death in the Battle of Tumhalad must have come as a relief to him.
Poor guy. I hope he found healing in the Halls of Mandos.

[Lalwendë]

Interestingly, PTSD can have an opposite effect to avoiding thinking about the events survived, it can lead to near pathological obsession with that type of event. For some time after my car accident (I like to think of it, grimly, as carnage) I was quite obsessed with watching anything about road accidents, these police programmes, news reports, even rubbernecking like crazy if I chanced upon a real one. I'm not saying I went as far as what JG Ballard writes about but in my own way, I was trying to find reasons for why this thing had happened to me.

It could be that Tolkien, through undertaking this enormous writing project, was dealing with this obsessive aspect of PTSD.

And for what it's worth, yes, I do think it's likely he suffered this to some extent, though not in a debilitating one, and he certainly knew enough about it to create Frodo who certainly displays the condition.

[William Cloud Hicklin]

There is no quotable proof of it, but I have wondered if "the Black Breath" that struck down so many who had fought the Enemy in LotR was symbolic of "shell shock" or "battle fatigue" in the old parlance, PTSD in today's terminology

Certainly this passage, referring not exactly to the Black Breath but the aura and cries of the Nazgul, was informed by what Tolkien observed in the trenches:

Out of sight and shot they flew, and yet were ever present, and their deadly voices rent the air. More unbearable they became, not less, at each new cry. At length even the stout hearted would fling themselves to the ground as the hidden menace passed over them, or they would stand, letting their weapons fall from nerveless hands while into their minds a blackness came, and they thought no more of war, but only of hiding and of crawling, and of death.