Capgras Syndrome is a delusional disorder whereby the sufferer believes that a friend, family member, spouse, or someone else they know has been replaced by an identical-looking imposter. Most commonly associated with Schizophrenia, the disorder has also been seen in brain injury and dementia.
It was first labeled in 1923 by French psychiatrist Dr. Joseph Capgras, whose patient believed “doubles” had replaced her husband and others she knew. (Thank you, Wikipedia, for that bit of information.) :)
Treatment includes medications such as anti-psychotics (Haldol, Zyprexa, etc).
What books or movies have you seen where a character believes others have been replaced by imposters?
Remember, these posts are for writing purposes ONLY and are NOT to be construed as medical advice or treatment.