Capgras delusion or Capgras syndrome is a psychiatric disorder in which a person holds a delusion that a friend, spouse, parent, or another close family member (or pet) has been replaced by an identical impostor. It is named after Joseph Capgras (1873–1950), the French psychiatrist who first described the disorder. The Capgras delusion is classified as a delusional misidentification syndrome, a class of delusional beliefs that involves the misidentification of people, places, or objects. It can occur in acute, transient, or chronic forms. Cases in which patients hold the belief that time has been "warped" or "substituted" have also been reported. The delusion most commonly occurs in individuals diagnosed with schizophrenia but has also been seen in brain injury, dementia with Lewy bodies, and other dementia. It presents often in individuals with a neurodegenerative disease, particularly at an older age. It has also been reported as occurring in association with diabetes, hypothyroidism, and migraine attacks. In one isolated case, the Capgras delusion was temporarily induced in a healthy subject by the drug ketamine. It occurs more frequently in females, with a female to male ratio of approximately 3∶2. From Wikipedia
