USATODAY.com - New 'Potter' movie sneaks in spoilers for upcoming books
USA Today quotes Rowling, from an interview released by Warner Bros.:
"[The Dementors] are just as frightening as I imagined, just superb," she says. "One of the biggest themes in the book is Harry's conquering the dementors. And the dementors for me were about depression, and not just sadness. I think Alfonso's really done a great job on that, in showing what that can feel like and the circumstance in which you become vulnerable to that."

