Even though I'm 26, I'll still get squeamish sometimes when it comes to horror in any medium, including video games. I just can't really deal with watching violent trauma to living things. I don't really get affected if it happens to monsters though.
My 1st horror-themed game was L4D2 at 19, and that's because I knew that it wouldn't be so scary if I was playing with other people. But My 1st solo experience with survival-horror was playing RE:Revelations 1 last year. It has since become one of my favourite games to play.