I think that humans are a pessimistic race at heart. Mothers assume that their children are in peril if they aren't home on time; if a husband is on a suspicious business trip, most wives would assume an affair. Sure these are stereotypes, but they still ring true, don't they?
Some people are optimists, some are outwardly optimistic but pessimistic inside, and then there are the rest of us. I think that no matter how many times we tell ourselves 'it will be fine, there's a good reason why they aren't where they said they'd be,' we are inclined to think the worst.
So what does that have to do with writing? And horror?
Well, a story is made not by what's there, but by what's not there. In other words, the reader has to read between the lines. This makes the reader feel special, because you have trusted them and not revealed everything just by telling it...you have implied it.
But a reader most often assumes the worst. If you speak of a suspicious business trip, the reader will infer that there is an affair.
This might not always be the case though.
Without telling them exactly word for word what's going on, how does one imply to achieve the correct inference from the reader? I can tell you this; it is hard.
So...to side-step this problem, writing dark stories where readers' pessimist assumptions are correct, are easier.
However, sometimes this pessimistic inference can be an advantage...for instance if the story sets up a wife (and reader) to think that the husband is having an affair, when in truth he is planning a surprise party. Neither the wife nor reader will know that their assumptions are incorrect until the last moment, and you have a story.
I think that explains why I write a lot of dark sort of horror stories for Magpie Tales...and it seems #7 is no different...