An investigation of the shocking mystery behind the dramatic experiment that revolutionized modern medicine, from the #1 New York Times bestselling author of Brain on Fire.

"Bold, brave, and original." —Susan Orlean, bestselling author of The Orchid Thief

Doctors have struggled for centuries to define insanity—how do you diagnose it, how do you treat it, how do you even know what it is? In search of an answer, in the 1970s a Stanford psychologist named David Rosenhan and seven other people—sane, healthy, well-adjusted members of society—went undercover into asylums around America to test the legitimacy of psychiatry's labels.

Forced to remain inside until they'd "proven" themselves sane, all eight emerged with alarming diagnoses and even more troubling stories of their treatment. Rosenhan's watershed study broke open the field of psychiatry, closing down institutions and changing mental health diagnosis forever.

But, as Cahalan's explosive new research shows in this real-life detective story, very little in this saga is exactly as it seems. What really happened behind those closed asylum doors?

Shortlisted for the 2020 Royal Society Insight Investment Science Book Prize
Named a Best Book of 2020 by The Guardian, The Telegraph, and The Times