At least IMDB and Amazon claim it is... I think I'll find out tonight.
It's one of those horror films that managed to perfectly plug itself into the world's subconscious. As I said in my review at the time:
"What Anna suffers is awful and unthinkable and evil, but it's awful and unthinkable and evil not because she randomly walked into the wrong campground but because the world is sometimes an awful, unthinkable, evil place, and because people can coldly and logically justify awful, unthinkable, evil things."
I don't believe I was even aware of the existence of the OLC memos when I wrote that.