I read Jaws when I was 10, and then the Fog (very bad) and then the Rats (worse, gave me nightmares). I got them from a friend at junior school, who'd nicked them off her big brother.
I carried on with the horror theme for a while, as well as far more wholesome fare (Anne of Green Gables style) - I was and still am a voracious reader. When I hit 18/19, I got bored/sickened by the whole horror genre and turned to historical warfare novels - RL horror, I suppose.
The Rats is something that still comes back to me every now and then, and a couple of scenes from the Fog; plus a few others.
Nothing in TP would touch me in the same way that those awful books did (actually, even Day of the Triffids and some Doctor Who stuff is worse!), I don't think.
And although the DV is bad, it's not unusual, is it, sadly. :(
I know MN has a skewed representation but I'm always quite horrified how many posters have DV in their backgrounds, either as children themselves, or with their current or ex P.
Anyway. I agree that if they can process the text, they are probably old enough to be able to ask about the topic and be given reassurances as necessary - they might not, however, be able to work through it themselves.