“Nothing dies so hard as a word”, wrote Harry Quilter in 1892, “—particularly a word nobody understands.” At the end of the nineteenth century, one such word—first uttered in America, but soon reverberating across the Western world—was “neurasthenia”. Popularized by the American neurologist George M Beard, this vaguely defined nervous disorder seemed to crop up everywhere, from medical journals to the popular press to belles lettres. Looking back at the years leading up to the Second World War, Paul Hartenberg recalled its remarkable pervasiveness: “It could be found everywhere, in the salons, at the theatre, in novels, at the Palace. It was used to explain the most disparate individual reactions: suicide and decadent art, fashion and adultery; it became the giant of neuropathology.” Its sufferers included American intellectuals from Beard himself to Theodore Roosevelt, Edith Wharton, and Henry Adams; for European commentators less convinced of the disease's modern American pedigree, the list could be expanded to include everyone from Alcibiades to Tiberius to Napoleon. Anybody who was anybody, it seemed, was neurasthenic.