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.