Capgras Syndrome: The Nightmarish Delusion That Your Loved Ones Have Been Replaced By Impostors

Also called Capgras syndrome, it has captivated fiction writers and scientists alike for generations, ever since its first description by French psychiatrists Joseph Capgras and Jean Reboul-Lachaux in 1923. 

They described the case of “Madame M.”, who came to the attention of authorities in June 1918 when she reported that her husband, daughter, police officers, and doctors had all been replaced, sometimes thousands of times over, by impostors. Consigned to psychiatric institutions, Mme M. was considered by Capgras and Reboul-Lachaux to be suffering from l’illusion des sosies, which translates as the “lookalike” or “doppelgänger” illusion. 

Since this first description, many further cases have come to light, and science has progressed in its understanding of the syndrome. 

What is Capgras syndrome?

There’s debate as to whether the true Capgras delusion only applies to family members, as a lot of case reports have focused on this aspect; however, Professors Max Coltheart and Martin Davies argued in a 2021 paper that this is too restrictive, and that hundreds of cases have involved the “replacement” of other notable people in a person’s life, just as Mme M. reported with the police and medics. 

Coltheart and Davies listed five potential subtypes of Capgras delusion, which they speculated could have similar underlying mechanisms, though they stressed that future research would need to confirm that:

• Belief that a close relative has been replaced by a stranger
• Belief that an acquaintance has been replaced by a stranger
• Replacement beliefs triggered by hearing the voice of a familiar person
• Replacement of a pet
• Replacement of a personal possession, e.g. believing that letters written by a loved one are actually forgeries

The idea of a Capgras delusion centering on a pet or inanimate object does have precedent in the literature. For example, a case report from 2015 discussed a 53-year-old woman whose Capgras delusion was brought on by medication taken for Parkinson’s disease. She became convinced that her pet dogs and the plants in her garden had been replaced by identical copies. 

A 2016 report told the story of a 73-year-old man who came to believe his pet cat had been replaced by a doppelgänger following a brain injury. 

A paper in 2023 discussing Capgras syndrome and other related disorders presented three cases of potential Capgras delusions directed at objects rather than people: one patient believed her kitchen utensils, shoes, and clothing items had been replaced with inferior versions; another was convinced that scenes in a favorite movie had been altered and replaced, and that her medications had been swapped for placebos; and the third believed that passages in books she enjoyed were being replaced with manipulated text.

The question of Capgras syndrome triggered by voice is more curious. Sometimes, even those who are actively experiencing Capgras delusions do not report them when they hear the person’s voice, only when they see their face. There are a few cases in the literature where, for instance, someone’s belief that a relative has been replaced by an impostor is strengthened when they feel their voice sounds different on the phone. 

But by far the most common examples of Capgras delusions in the literature are visual and refer to close family. 

It’s easy to imagine how distressing and frightening these experiences must be – it speaks to deep fears around being able to trust the evidence our eyes are showing us, not being believed when we feel something is deeply wrong, as well as the very human discomfort with the uncanny valley – where things appear familiarly human, but just not quite enough.

It also ties in with dark folkloric tales of changelings. Legends from many European cultures, which persisted for centuries, tell of children being kidnapped and replaced by the offspring of mythical beings like fairies. While these beliefs may not fall under the definition of Capgras delusions, at least not in every case, the conviction that something wasn’t right could be so strong as to lead to devastating consequences. It was believed by some that torturing the “changeling” could bring the original child back – beliefs that led to instances of actual child abuse. 

For one 28-year-old in Colombia experiencing a true Capgras delusion, the distress almost led to the unthinkable. A case report in 2022 detailed how the man, becoming convinced that his parents had been killed and replaced by impostors, attempted murder against a neighbor, whom he blamed for orchestrating the replacement. 

What do we know about the causes of Capgras syndrome?

There’s no single cause of Capgras delusions, which is partly why it’s been difficult to know whether all of the very different presentations are types of the same disorder or completely separate phenomena. 

In some cases, psychiatric disorders such as schizophrenia may be the underlying cause. All three patients in the 2023 study of Capgras delusions around inanimate objects had long histories of symptoms that suggested paranoid schizophrenia. 

Other cases are associated with neurodegenerative disease. The Lewy Body Dementia Association explains that delusions are a common symptom of both Parkinson’s disease dementia and dementia with Lewy bodies, and these delusions can take the form of Capgras syndrome. 

As with the patient who believed her dog and plants were being replaced, sometimes the medication given to treat the movement symptoms of Parkinson’s disease is the cause, and may need to be decreased. Antipsychotic medications can also be effective at treating the delusions. 

Capgras syndrome may also be brought on by a brain injury, as was the case with the man who believed an imposter had replaced his cat. 

An unusual case reported in 2016 involved a male patient in his 30s who had sustained a serious traumatic brain injury in a road accident. Following severe damage to areas of the right hemisphere of his brain, the patient experienced the delusion that his wife had been replaced by an impostor, as well as a rare tactile hallucination – he felt as though he was constantly wearing a vest, whether or not there was any clothing over his chest at all. 

A 2019 review of 255 English-language reports of the syndrome concluded that “schizophrenia remains the largest single disorder associated with case reports of Capgras’ delusion,” but it was by no means the only important cause. 

Early hypotheses suggested that there could be a link between Capgras syndrome and prosopagnosia, commonly known as face blindness. But the authors of the review explain that this was soon put to bed. Prosopagnostics still show emotional responses to familiar faces; they just have difficulty assigning a specific face to a specific person. Those with Capgras syndrome, on the other hand, don’t see the faces as familiar at all. 

One silver lining the authors do highlight, however, is that “most sufferers can expect a good response to antipsychotic medication, irrespective of aetiology.” There is hope for relief from the distress that Capgras syndrome undoubtedly causes.