Ganser syndrome is a rare and controversial mental disorder that is characterized by a person's answer to a simple question that appears to be deliberately wrong, inappropriate or absurd. Also known as prison psychosis, nonsense syndrome or syndrome of approximate answers, it often occurs in individuals who are under extreme stress or have been subjected to a traumatic experience. The condition is named after Sigbert Ganser, who first described it in the late 19th century. Although it is not officially recognized as a distinct mental illness in the Diagnostic and Statistical Manual of Mental Disorders, the term Ganser syndrome is often used to describe similar conditions such as pseudodementia, hysterical neurosis or dissociative disorder.