The phrase Paris syndrome denotes the culture shock experienced by an individual—typically a Japanese—who, when visiting, or living in, Paris, the capital of France, realises that this city does not fulfil his/her idealised expectations.

This phrase is apparently a loan translation from Japanese Pari shōkōgun, coined by Hiroaki Ōta, a Japanese psychiatrist who was based in Paris and authored Pari Shōkōgun (Tokyo: Toraberu Jānaru, 1991).

The earliest occurrences of the phrase Paris syndrome that I have found are from Mon Dieu! Those Parisians are so rude, by Robert Melcher, published in The Age (Melbourne, Victoria, Australia) of Sunday 12^th January 1992:

Life in Paris is becoming a nightmare for thousands of foreigners. Special help-lines have been set up and psychiatrists have been inundated by people suffering from isolation and rejection.
One Japanese counsellor has dubbed the phenomenon the “Paris syndrome”. It is brought on by the notorious Parisian arrogance. This is exacerbated by the language barrier, the culture shock and the rudeness.
It seems that the French themselves agree. In a recent national survey, 31 per cent said Parisians topped the most-hated category of people in France. They were way ahead of civil servants at 21 per cent, Corsicans at 23 per cent and policemen at 18 per cent.
Sociologist and author Gerard Mermet says: “The French themselves realise that courtesy and respect for others are on the decline. The deterioration of the social atmosphere is especially felt in the bigger cities.
“Car drivers are often aggressive, shop assistants unmotivated and administrative workers arrogant. This has a negative effect on foreigners’ perception of French and the French.”
Mermet believes that “the mixture of attraction and repulsion that some foreigners feel for France can be explained by the contrasted character of a nation torn between past and present, tradition and high technology—between the will to succeed and the wish for comfort”.
[…]
Sociologist Serge Tame says […] that Parisian hostility and rudeness are not particularly directed against foreigners. They are directed against everyone.
“Most people who live and work in Paris are not true Parisians. They come from the provinces seeking jobs and better lives, and they are often just as uprooted, lost and confused as any foreigner. The only difference is that they speak the same language and share the same culture.
“So they soon learn that, in order to survive in Paris, they must be just as aggressive and disagreeable.”
[…]
There is a joke, seldom told in Paris, about the true reason for Parisians. It is said that when God created the earth, he decided to create a beautiful country. He named it France. But when the people of the world saw what He had done, they became angry. So, in order to compensate, God created Parisians.
This sort of humor may not help cure anyone of the Paris syndrome, but its thousands of restaurants, cafes, cinemas, museums, theatres, parks, monuments and night clubs might.
Paris is still one of the most enchanting cities in the world. No one ever said it was also charming.

The following interesting article was published on Sunday 26^th December 2004 in the Sunday Tribune (Dublin, County Dublin, Ireland):

Japanese expats hit by Paris Syndrome

Hugh Schofield
Paris
First there was the Stockholm Syndrome, then there was the Jerusalem Syndrome, now psychiatrists have discovered the Paris Syndrome. But don’t worry: you are not at risk unless you are young, female and Japanese. According to Dr Hiroyki [sic] Ota, a Japanese national who works at the Sainte Anne hospital in Paris, more than 100 people pass through his consulting room every year exhibiting the same symptoms of nervous depression.
Around a quarter of them have to be hospitalised before being sent home. In The Paris Syndrome, he explains the progression of the disorder: first mild anxiety, then a growing persecution complex, fear of leaving home, despair and sometimes even suicide.
The cause is always the same: a bad social experience with a Parisian, triggering a profound sense of cultural alienation. “The phenomenon is most common among those Japanese who prove themselves incapable of adapting to France because of a shock set off by a confrontation between the two cultures,” Ota says.
The Japanese have long had a love affair with Paris, nurtured by dreams of sophisticated manners coupled with physical elegance, exquisite food and lots of Louis Vuitton handbags. Most of the 28,000 Japanese residents of France live in the capital, which is visited every year by millions more. What they find though is not always what they had been led to expect. “Often the people I show around are extremely disappointed,” said Akira Hasegawa, a Japanese tour guide who has been working in France for 15 years.
“They think Parisians are going to be clean and polite and friendly—and it’s the exact opposite. What they want is the old France—full of people like Jean Gabin and Alain Delon—but it’s not like that at all. You British have the same experience, no?” he says.
Nearly all of the victims of Paris Syndrome are women, who tend to be more besotted with the city’s romantic image than men. Press coverage of the French capital in Japan invariably plays up the “city of light” cliché, and the fact several Japanese television and screen celebrities have chosen to settle there boosts the wannabe factor.
It comes as no surprise to learn that for many young Japanese the most shocking discovery is the Parisians’ legendary rudeness. For visitors from a country where relations between individuals are subject to a strict social code, the ordeal of being ignored by a surly waiter—or having a post office clerk deliberately misunderstand your attempts at French—must be painful indeed.
However, Bernard Delage, a Frenchman who runs the Association Jeunes Japon, argues things today are at least better than they used to be.
“Up till 15 years ago it was really very hard to be Japanese in Paris. Everyone took them for Chinese—which they hate—and because they were rich back then before the recession, they were ripped off wherever they went,” said Delage, who helps Japanese executives and students settle in France.
“Today the problem is with a relatively small number of girls—spoiled types who come out with daddy’s money to experience the freedom. But they find they can’t cope. The same thing happens wherever the Japanese go abroad. For them other countries are always a cultural shock.
“What’s different in Paris is that they come here loving it more than anywhere else, secondly, Parisians are indeed unusually awful.”