I was four the first time I saw a ghost...at least, that's as early as I can remember it anyway. And they're never- I mean, they always look like they did at their death. People don't stick around just because they died in their sleep, yanno? It's always like something out of a horror movie. Blood everywhere, organs or brain matter half falling out, muscles showing under flayed skin-- whatever it is. Half of the time they look like fucking zombies.

And I dunno, it took awhile for my dad to believe me about what I was seeing. I couldn't prove it, really, I don't even remember why he finally did believe me. But you know, your parents- they're supposed to save you from the monsters under your bed, but not my dad. My dad just threw me at them harder.

[He takes in a soft, slightly shuddering breath at the memories he's dragging up. But it doesn't feel impossible to talk about, at least. That feels like some kind of progress, somehow.]

I think I was... six? Maybe seven, the first time he locked me in the crypt. I couldn't escape the dead on a good day, but in there-- [He shakes his head.] I was cornered from every direction by these shrieking, grotesque spirits that pawed at me and screamed my name, and I didn't know what they wanted, I didn't know what my dad wanted, and he left me. He just fucking left me there alone and locked in the mausoleum until dawn. And he did it for years, until I finally left home.

[tl;dr answer to your question, Harlan: Trauma, mostly.]