The Jerusalem Syndrome is a form of temporary psychosis that effects people of certain religions background while visiting or touring the city of Jerusalem.
Jerusalem Syndrome typically involves a person with no prior signs of mental illness visiting the city and then experiencing an extreme psychotic or delusional episode. One of the most popularly reported delusions is the belief that a person is the Messiah or the second coming of Christ. The syndrome primarily effects people of Jewish, Christian, and Muslim backgrounds. People of other faiths and or atheists tend to be immune. Luckily, the delusion or psychosis tends to disappear within a few weeks to months after leaving Jerusalem.
It should be noted that there is some controversy as to whether or not Jerusalem Syndrome is a valid phenomenon. Certain critics suggest that the people effected by the syndrome were mentally ill prior to their coming to Jerusalem.
The Jerusalem Syndrome has inspired a musical by the same name and was even used in an episode of The Simpsons in which Homer believes himself to be the Messiah after visiting the holy city.
The Jerusalem Syndrome
The Jerusalem Syndrome: Why Some Religious Tourists Believe They Are the Messiah