The syndrome of subjective doubles is a rare delusional misidentification syndrome in which a person experiences the delusion that he or she has a double or Doppelgänger with the same appearance, but usually with different character traits and leading a life of its own. Sometimes the patient has the idea that there is more than one double. The syndrome is usually the result of a neurological disorder, mental disorder or some form of brain damage, particularly to the right cerebral hemisphere. In some cases, the syndrome (also referred to as syndrome of Christodoulou) may be the result of delusional elaboration of autoscopic phenomena.
Sometimes the delusion takes the form of a conviction that whole or part of the patient's personality has been transferred into another person. In this case depersonalization may be a symptom. One example from medical literature is of a man who became depersonalized after an operation and was convinced his brain had been placed into someone else's head. He later claimed he recognized this person.
The syndrome is sometimes comorbid with Capgras delusion, leading to it to be named "subjective Capgras syndrome" in some instances.
In the novel and film Youth in Revolt, protagonist Nick Twisp exhibits characteristics of the Subjective Doubles Syndrome. His delusion takes his form, adopting the name François. Though the film did not make it apparent as to whether or not Nick had experienced brain trauma or possessed any neurological disorders, his alter-ego was shown to be a version of himself entirely independent and largely influential. In spite of François's questionable tactics, it cannot be claimed that he is a Doppelgänger, in its traditional sense, since he is ultimately out for the success of his "creator."{{Or|june 2011|date=June 2011}
The case could also be made that Nina Sayers (Natalie Portman) from the film Black Swan experienced this, perceiving the people around her as different versions of herself.