Entity cleansings a physical body dies and the spirit transitions to the spirit realm without complication. When for whatever reasons, the spirit does not transition to the other side, it remains stuck among the living. When the spirit lingers it begins to lose energy and its sense of self- preservation kicks in. It needs more energy to survive and starts stealing energy from living persons. Which can make the living person start to self-destruct, by alcohol abuse, eating disorders, and more.
In order to make a change the entity has to be removed. That can be done by several visits to cleanse the home.