I never perceived Paris as a particularly welcoming or friendly city, and I imagine few people do. All the things you read about the Gallic Shrug and general rudeness are absolutely true there, but I found you can have amazing fun if you just choose to be entertained by it instead. In the end, it all boils down to the fact that in Paris, nobody will help you with anything. On the other hand, it's mostly a city where you don't actually need a lot of help to get by. If you can manage to blend in and not care about strangers, it's quite a fun place.

The article itself portrays very well that Paris syndrome is probably not real (in a statistical sense). There is a big number of tourists in the city at any given moment, some of them will statistically snap during their stay. I do like the theory that disillusionment and added stress contribute to the timing, though - especially if the trip was expensive.

Since the article mentions it, Jerusalem syndrome is similar but qualitatively different. Many people who go there are not just tourists. I'd wager that for over 90% of travelers there the city has some kind of religious significance. They are essentially pilgrims. And you'd have to be to want to go there: the city itself is a dirty, oppressive mess filled with scary people and shady salesmen.

Combining these factors, it wouldn't surprise me if the incidence of Jerusalem syndrome was much higher than Paris, mostly due to the clientele but also the city itself.

Now Stendhal syndrome is more interesting: it's a generalized description of these kind of psychotic breaks, though they are mostly understood to be a little bit more benign than Jerusalem syndrome. By definition, these effects are attributed to exposure of a susceptible individual to an object of great personal importance, such as a piece of art. In this context, the same pattern of breakdowns has been studied with tourists who snap while visiting Florence.