a disorder in which a person holds a delusion that a friend, spouse, parent, or other close family member has been replaced by an identical-looking impostor. it 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 is most common in patients diagnosed with schizophrenia, although it can occur in connection with a number of conditions, including brain injury and dementia. it has also been reported as occuring in association with diabetes, hypothyroidism and migraine attacks. it occurs more frequently in females, with a female:male ratio of 3:2.