Around a dozen Japanese tourists a year need psychological treatment after visiting Paris as the reality of unfriendly locals and scruffy streets clashes with their expectations, a newspaper reported on Sunday.

"A third of patients get better immediately, a third suffer relapses and the rest have psychoses," Yousef Mahmoudia, a psychologist at the Hotel-Dieu hospital, next to Notre Dame cathedral, told the newspaper Journal du Dimanche.

Already this year, Japan's embassy in Paris has had to repatriate at least four visitors -- including two women who believed their hotel room was being bugged and there was a plot against them.

Previous cases include a man convinced he was the French "Sun King", Louis XIV, and a woman who believed she was being attacked with microwaves, the paper cited Japanese embassy official Yoshikatsu Aoyagi as saying.

"Fragile travellers can lose their bearings. When the idea they have of the country meets the reality of what they discover it can provoke a crisis," psychologist Herve Benhamou told the paper.

The phenomenon, which the newspaper dubbed "Paris Syndrome", was first detailed in the psychiatric journal Nervure in 2004.

Bernard Delage of Jeunes Japon, an association that helps Japanese families settle in France, said:

"In Japanese shops, the customer is king, whereas here assistants hardly look at them ... People using public transport all look stern, and handbag snatchers increase the ill feeling."

A Japanese woman, Aimi, told the paper:

"For us, Paris is a dream city. All the French are beautiful and elegant ... And then, when they arrive, the Japanese find the French character is the complete opposite of their own." (Yahoo! News, via Reddit)