The Capgras delusion (or Capgras syndrome) is a rare disorder in which a person holds a delusional belief that an acquaintance, usually a spouse or other close family member, has been replaced by an identical looking impostor. The Capgras delusion is classed 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.
The delusion is most common in patients diagnosed with schizophrenia, although it can occur in a number of conditions including after brain injury and dementia. Although the Capgras delusion is commonly called a syndrome, because it can occur as part of, or alongside, various other disorders and conditions, some researchers have argued that it should be considered as a symptom, rather than a syndrome or classification in its own right.
It is named after Joseph Capgras (1873-1950), a French psychiatrist who first described the disorder in a 1923 paper by Capgras and Reboul-Lachaux. They used the term l'illusion des sosies (the illusion of doubles) to describe the case of a French woman who complained that various "doubles" had taken the place of people she knew. However, the term illusion has a subtly different meaning from delusion in psychiatry so "the Capgras delusion" is used as a more suitable name.