Each year, approximately 20 Japanese tourists are struck down by a rare and mysterious disorder.

At least 19 of them will be idealistic young women in their early 30s. They will suffer acute, gnawing anxiety, breathlessness, and then deep depression. They will be stretchered to airplanes for the only known cure, which is to return to Japan and never again set foot in the French capital.

Paris Syndrome, as the condition is known, is an amusing phenomenon with a very real provenance. According to psychiatrist Hiroka Oka, who first documented the affliction some 20 years ago, the root cause is a mismatch between deeply romantic Japanese expectations of Paris, and what it actually delivers.