Religious persecution may be part of a social, political or economic conflict between two religious groups which may conduct terrorist activities against each other. Force or superior power may be used to exploit a different religious group through fear. This may be achieved by physical or psychological intimidation, terrorism, indoctrination and occultism. Indoctrination and moralism may produce a guilt complex. Fear of the occult and of being cursed may cause mental disorder, physical disease and even death (as is recorded in tribal societies).