The whole atmosphere of the film itself is very uncomfortable and a few scenes will definitely make you jump. The cannibals are very scary. There's a scene where a Finn speaks about "traditions" which is present in a darkly comedic way, but may creep out some people a little. There are pretty many scenes where the mother and her son is arguing with each other, which can be very emotional or sad.
(Deleted. Personal opinions about ratings are not appropriate for the Parents Guide.)