Jerusalem syndrome

In the city of Jerusalem, there is a special ward in the mental hospital for those who represent a special danger to themselves and others. These deluded patients are the sufferers from the "Jerusalem syndrome." Police and security officers are trained to recognize them, though their mania is often concealed behind a mask of deceptively beatific calm. They have come to the holy city in order to announce themselves as the Messiah or redeemer, or to proclaim the end of days. Jerusalem syndrome is a rare psychiatric disorder described by Dr Gregory Katz (head of the Emergency Unit at the Givat Shaul Mental Health Centre) in the British Journal of Psychiatry in 2000.

Sufferers arriving in Jerusalem are afflicted with the delusion that they are characters from the Bible, the Torah, or the Koran, or are, in some other sense, a messianic figure.

Clinical definition
Dr. Katz described 7 stages:

The Israeli police have set up a special unit to deal with such people and between 30 and 40 people a year are admitted, but only a few are diagnosed as having "genuine" Jerusalem syndrome. Bar-El et al. reported 42 such cases over a period of 13 years, and none of these cases seemed temporary in nature — thus, to be considered "genuine" Jerusalem syndrome.

Most patients are middle aged from small towns in the USA or Scandinavia. Jet lag and lack of sleep could possibly be contributing factors, though travelers from Scandinavia barely leave their timezone.

The inherent link between religiosity and mental illness
The late Christopher Hitchens doesn't fail to put the Jerusalem syndrome in context to the concept of revelation and an invisible being who influences people, writing on the topic of the syndrome:

Rationalizations by the faithful
Because there are so many self-proclaimed messiahs arrested every year, rabbis had to define the messiah to exclude such people, without unintentionally condoning the arrest of the real messiah, should he appear. Their official explanation is that, by definition, the real messiah will be self-evident, and everyone will automatically know he is such. (This position, interestingly, disqualifies Jesus from being the messiah, because there were those who met him and still doubted him (e.g., the Sanhedrin and most Roman officials), but Jews don't believe Jesus was the messiah in the first place so whatever.)