Did a lot of people not get the theme?

Simply put: depression. ?

they weren't too subtle with the theme, i doubt many people didn't get it. just doesn't makes the story that much better ;) i enjoyed the movie but it had lots of boring scenes and in my opinion tried to be much more deep than it turned out to be. the backstory of Diana was too thin, i would've liked to find out more about that and less about the romance between Becca and her boyfriend.
but i don't expect much from these kinds of movies so i guess it was okay. a little cheesy at the end, but better than the planned ending where Diana comes back and attacks in the last scene ;)

"Angel Investigation - we hope you're helpless" - Doyle

Wow. There is little to nothing about this movie that isn't given to the audience on a silver platter. It's not that the movie's themes weren't obvious..it just doesn't make it a good movie..

I did wonder if this movie was going to have a pro pharmaceutical message in it, but gladly they didn't step over the mark.

Really deep stuff here. The metaphor is subtle. Your psychological issues appear when you are in the dark of self delusion, but disappear when you shine the light of therapeutic evaluation. A change in perspective, like a UV lamp, will put the problems into focus, but won't solve them. Employing half measures, like shooting at the ghost with bullets, is not effective. If untreated, your psych issues can ruin your life, such as murdering police officers.

*Here's a ****in' spoiler: Everybody dies.*

I try not to think about the deeper psychological commentary happening here because the ending would be absolutely thoughtless and disgusting if read in that light.

No, the only solution to depression is not to blow your brains out in front of your children.