What does it feel like to go insane and not know why? In her memoir, Brain on Fire: My Month of Madness, author Susannah Cahalan describes what it is like in terrifying detail: “My body continued to stiffen as I inhaled repeatedly, with no exhale. Blood and foam began to spurt out of my mouth through clenched teeth.… This moment, my first serious blackout, marked the line between sanity and insanity. Though I would have moments of lucidity over the coming weeks, I would never again be the same person. This was the start of the dark period of my illness, as I began an existence in purgatory between the real world and a cloudy, fictitious realm made up of hallucinations and paranoia.”