Cotard's syndrome

Cotard's syndrome, also known as Cotard's delusion or walking corpse syndrome, is a rare mental disorder in which the affected person holds the delusional belief that they are deceased, do not exist, are putrefying, or have lost their blood or internal organs. Statistical analysis of a hundred-patient cohort indicated that denial of self-existence is present in 45% of the cases of Cotard's syndrome; the other 55% of the patients presented with delusions of immortality.

In 1880, the neurologist and psychiatrist Jules Cotard described the condition as le délire des négations ("the delusion of negation"), a psychiatric syndrome of varied severity. A mild case is characterized by despair and self-loathing, while a severe case is characterized by intense delusions of negation, and chronic psychiatric depression.