The disappearance of Oliver McAfee, a 29-year-old British tourist who was last seen in November, has raised the possibility that he may be suffering from a disorder known as Jerusalem syndrome. McAfee had been cycling through the Negev desert in southern Israel, and a search was started after hikers found his wallet and laptop. The Telegraph reports that a trail of pages torn from the Bible were found, along with notes McAfee had made, which led investigators to believe he had deliberately gone into the desert – there were references to the story of Jesus going into the desert for 40 days and 40 nights. It has been suggested that McAfee, reportedly a devout Christian, may have developed Jerusalem syndrome, where people experience religious delusions.

It used to be more common, with about 50 cases each year – enough for a psychiatric hospital in Jerusalem to become the designated treatment centre for tourists, mostly Christian, in the grip of the condition. There was a spike in reported cases in the run-up to the millennium, but in an interview in 2011, a psychiatrist at the hospital reported seeing only two or three cases a year.

It has become a curiosity, played for laughs in an episode of the Simpsons (on holiday in Jerusalem, Homer becomes convinced he is the Messiah), but it is often disturbing and dangerous for those afflicted, many of whom are hospitalised. In 1969, Denis Michael Rohan, an Australian tourist, set fire to the al-Aqsa mosque, believing he was on a divine mission. His actions caused riots across the city. There have been men convinced they were Jesus or John the Baptist, and women believing they were the Virgin Mary.

Israeli psychiatrist Yair Bar-El, an expert on the condition, co-wrote a paper for the British Journal of Psychiatry in 2000 that described those affected. Most people who experience it have underlying psychiatric illnesses, such as schizophrenia – which drove their decision to travel to holy sites in the first place, perhaps in some kind of messianic quest – or a condition such as a personality disorder. More controversial is the idea of “true” Jerusalem syndrome – that otherwise healthy people with no history of mental illness, can arrive in Jerusalem as a regular tourist and become disturbed. Between 1980 and 1993, there were just 42 patients who fitted this category, though what almost all had in common was coming from “ultra-religious families”.