In the early 19th century, an 18-year-old woman known as Mademoiselle F. was walking home from her aunt’s house when she suddenly thought, what if she’d stolen something from her aunt? She hadn’t, but the thought kicked off an all-consuming obsession that eventually drove her to extreme measures to prevent herself from stealing. Mademoiselle F. was the first documented case of obsessive-compulsive disorder, or OCD. Nowadays it affects up to three percent of the population. Journalist David Adam is part of that statistic, and his new book about the disorder is called The Man Who Couldn’t Stop: OCD and the True Story of a Life Lost in Thought.