'Haunted' the Disadvantage - what book is it in?

[Christopher R. Rice]

Originally Posted by sir_pudding

Christine in particular has panic attack symptoms throughout the episode, which aren't a specific GURPS disadvantage, although some combination of Post Combat Shakes and Mild Flashbacks probably work.

GURPS Horror introduced Panic Attacks on p. 27.

I'd call what Joseph is experiencing Flashbacks - that is what is occurring. Probably a quirk or maybe the -5 point advantage.