…by the shocking rudeness of French waiters and taxi drivers. Apparently a large enough number of innocent Japanese tourists, heads filled with romantic visions, find the grim realities of Paris so devastating to their fragile, polite psyches that a name has been given to the condition–"Paris Syndrome."
The Japanese embassy, a handful of times a year, apparently has to send their mentally strained citizens back to the homeland with doctors and nurses aboard to mind them. As with any "syndrome" that is in fact an understandable, if eccentric, reaction to circumstances, the "cure" is–to get out of Paris and don't come back.
The far more interesting "Jerusalem Syndrome"–religious delusions suddenly overtaking travelers to the Holy Land–discussed here.