A lot of indigenous cultures are deeply involved in working with ancestor spirits, elemental spirits, and demons. Many of these cultures feel that, if you don't deal properly with ancestor spirits, then they come back and infest the living in the form of things like depression, addictive patterns, and neuroses. We in the modern West completely deny the existence of these spirits or other types of entities. And because we've denied them, we may have opened the gates for them to manipulate us in a lot of ways.