In This Book May Cause Side Effects, Dr. Helen Pilcher explores the “nocebo” effect—the shadow side of the placebo—and shows how our convictions can sometimes quite literally harm usTake the COVID vaccine. If you experienced side effects from your COVID vaccine, there is a 76% chance that these were caused by your belief that you would experience them—not by the mRNA circulating your system. Or, even more extreme, take the case of Sam Shoeman: Although his diagnosis of late-stage esophageal cancer turned out to be erroneous, he was nonetheless dead in months. The power of words, especially from health-care providers, is so formidable that even a wrong diagnosis can actually kill. Our health, or lack of it, is as much about our expectations about illness and its causes as it about damaged cells or wayward hormones. And because we can never fully step outside our cultural context, it’s only by understanding these effects that we can hope to prevent them.This Book May Cause Side Effects explores a range of contemporary and historical examples of the nocebo effect, from “hex deaths” to TikTok “illfluencers” to functional neurological disorders, or real illnesses with real symptoms that nonetheless lack any kind of physical basis. Although the nocebo effect has always existed, the advent of the Internet has accelerated its spread. Thankfully, though, Dr. Helen Pilcher also walks us through steps we can take individually and culturally to avoid invoking the nocebo, like reevaluating our relationship to technology, setting up risk-minimizing guidelines in health-care settings, and even crowbarring open-label placebo therapies and nocebo-blocking medicines into the pharmacological toolkit. This Book May Cause Side Effects tells us that though our own minds construct the nocebo effect, it is also in our power to stop it.