When journalist Peter Andrey Smith attended the 2017 World Happiness Summit in Miami, he asked everyone he met, “Who’s the happiest person here?” Many, he reported, pointed to themselves and said, “Me.”

A late nineteenth-century concern for the nerve-racking speed of modern life prompted neurologist George Beard to introduce the term neurasthenia for a sickness whose symptoms include headaches, anxiety, impotence, insomnia, and lack of ambition. The condition was so prevalent in the United States that William James—who received the diagnosis along with his sister, Alice—referred to it as Americanitis.

President Herbert Hoover once praised a group of PR professionals. “You have taken over the job of creating desire,” he said, “and have transformed people into constantly moving happiness machines—machines which have become the key to economic progress.” It was 1928; the Great Depression began the following year.