Imagine you wake up in a hospital without a single memory of the last month. Doctors say you had a series of violent episodes and paranoid delusions. You'd become convinced you were suffering from bipolar disorder. Then, after a special test, a neurologist diagnoses you with a rare autoimmune disease called anti-NMDAR (Anti-N-methyl-d-aspartate receptor) encephalitis. This is what happened to Susannah Cahalan, a New York Post reporter who would go on to write the best-selling memoir Brain on Fire: My Month of Madness.

Imagine you wake up in a hospital without a single memory of the last month. Doctors say you had a series of violent episodes and paranoid delusions. You’d become convinced you were suffering from bipolar disorder. Then, after a special test, a neurologist diagnoses you with a rare autoimmune disease called anti-NMDAR (Anti-N-methyl-d-aspartate receptor) encephalitis. This is what happened to Susannah Cahalan, a New York Post reporter who would go on to write the best-selling memoir Brain on Fire: My Month of Madness.

Anti-NMDAR encephalitis can lead to hallucinations, blackouts, and psychosis, says Cold Spring Harbor Laboratory Professor Hiro Furukawa. It mostly affects women ages 25 to 35—the same age at which schizophrenia often presents itself. But what’s happening in anti-NMDAR encephalitis is something else.