Susannah Cahalan is an American writer and author best known for her memoir Brain on Fire: My Month of Madness, which chronicles her hospitalization with anti-NMDA receptor encephalitis, a rare autoimmune disease. The book brought significant attention to this condition and her personal experience with it. Beyond her debut memoir, Cahalan has published additional works exploring themes related to mental health and psychology. Her second book, The Great Pretender: The Undercover Mission That Changed Our Understanding of Madness, was published in 2019. In 2025, she released The Acid Queen: The Psychedelic Life and Counterculture Rebellion of Rosemary Woodruff Leary. In addition to her book writing, Cahalan works as a writer for the New York Post. Through her various writing projects, she has helped raise awareness about brain disease and mental health topics.