poltergeists are said to bother only one person at a time. this person is called their "focus". poltergeists will bother only their focus. they are said to only last a few weeks, then will move on to another target. often poltergeists are reported around children and adolescents. some scientists think that poltergeists only exist in a person's head as a result of psychokinesis. they think that the "poltergeist effect" is a result of mental trauma.