About 3/4 through, the head of a dead horse appears abruptly. Then the camera pans to show many other dead horse bodies in different states of decay. When you see Martha walk into the barn looking for Cleaves, that's your clue to cover your eyes. Time code is 01:10:45 - 01:10:58.
At the end of the film, Boyd is pitted against both the hunger and Ives and willingly subjects himself to a bear trap. Though perhaps not typical self harm, some measure of control is taken to harm himself intentionally
Boyd suffers from PTSD and commits violence throughout the film, but almost always out of self-preservation, and it is never presented as being a result of his PTSD or mental struggles.