A new study finds that people who report having had near-death experiences (NDEs) also have elevated levels of carbon dioxide in their blood—indicating that they might be suffering from oxygen deprivation. Researchers studied 52 heart attack patients, of which 11 reported having NDEs, “such as movement toward a bright light, feelings of peace and joy, and profoundly spiritual moments during their heart attacks.” The 11 patients who had experience NDEs were found to have more carbon dioxide in their blood than the rest.