The Placebo Effect’s Evil Twin (Michael H. Bernstein, 3/11/24, Quillette)

The term “nocebo effect” derives from the Latin word nocere, which translates roughly as “to harm” (as in the Hippocratic injunction, primum non nocere—first, do no harm). Whereas the better-known placebo effect is typically positive (the alleviation of pain or malaise through treatments that otherwise have no inherent therapeutic value); the nocebo effect is negative, often manifesting as headache, skin irritation, or nausea.

No surprise, then, that the nocebo effect has been called “the placebo effect’s evil twin.” It can be more formally summarized as “the occurrence of a harmful event that stems from conscious or subconscious expectations.” Or, more simply: When you expect to feel sick, you are more likely to feel sick. […]

The mind’s unfortunate ability to create suffering ex nihilo can sometimes affect large groups of people though a process of social contagion (or, in the more indelicate language of the past, hysterical contagion). One such example, known as “The June Bug,” occurred in a U.S. textile mill in 1962. Many employees began to feel dizzy and nauseous. Some vomited. Rumors of a mysterious bug that was biting employees began to circulate, and eventually 62 workers became ill. Yet a subsequent Centers for Disease Control and Prevention investigation determined that no bugs could be identified. Nor could investigators find any other physical cause of the illnesses. This type of phenomenon is now referred to as psychogenic illness—sickness caused by belief.

Over the course of history, there have been countless other examples of psychogenic illness, with symptoms ranging from hysterical laughter to seizures. Aldous Huxley, the famed author of Brave New World, described one such seventeenth-century example in his lesser-known historically-based novel, The Devils of Loudun. In the 1630s, as Huxley documents, an entire convent of Ursuline nuns in the western French community of Loudun became convinced that they’d been demonically possessed (complete with convulsions, and other symptoms recognizable to any connoisseur of the modern exorcism-themed horror-movie genre) due to the unholy machinations of a (genuinely licentious) local priest named Urbain Grandier.

Could such a mass outbreak occur today, in an era when few believe in demonic spirits? Consider that during 2016 and 2017, no fewer than 21 American diplomats serving in Cuba reported a range of bizarre neurological symptoms that later came to be collectively described as “Havana Syndrome.” News of the outbreak spread globally through American diplomatic networks, and eventually more than 200 U.S. diplomats became ill. One leading theory was that the Russian government was attacking American embassies and consulates with microwaves.