Throughout time and across cultures, people have faced an eternal question: Are people really who they say they are? This question manifests in everything from gut feelings about coworkers to relationship-damaging mistrust. But nowhere is this phenomenon more extreme—or stranger—than in the case of Capgras syndrome, a condition in which people believe that loved ones have been replaced by identical imposters. This seemingly unusual delusion is startlingly common: It affects up to 20 percent of people with Lewy body dementia and Parkinson’s disease dementia, and up to 10 percent of those with Alzheimer’s disease.

The disorder is primarily visual. A person with CS who strongly believes the person they are looking at is an imposter may not question that person’s identity over the phone.

About 12 to 18 percent of people who experience Capgras syndrome think they know who replaced their loved one, with family members, friends, and police officers being named as offenders. The delusion may last a few days or a decade.

Impact on the caregiver

Not only is this delusion traumatizing for the person experiencing it, but it is stressful, and even dangerous, for the caregiver, too. In a 2019 review of 255 cases of Capgras, 32 percent of people committed some form of aggression, and 4 percent committed homicide.


The most common neurological conditions associated with Capgras are brain trauma, dementia (Lewy body, Alzheimer’s, etc.), and organic delusional disorder. Interestingly, damage to the right hemisphere of the brain may be specifically relevant. The right hemisphere, and particularly the right frontal lobe, facilitates a sense of identity. However, Capgras delusions can occur in patients with impairments to both hemispheres.

The cause of the delusion isn’t clear, but a prevailing theory is the two-hit model. First, the cognitive disturbance that comes from something like Alzheimer’s disease leads to a delusional thought. Damage to the right hemisphere, especially the right frontal lobe, appears to be implicated in these delusions. But it takes a second “hit” to make the delusion stick: an impairment in a person’s ability to evaluate the plausibility of the delusion.

Underlying medical conditions may also play a role. Researchers reported in Neurology Psychiatry and Brain Research that a woman with Capgras who had a B12 deficiency showed significant clinical improvement with B12 replacement and 30 milligrams per day of aripiprazole. Other contributors may include mental illness, thyroid disorder, and drug or alcohol use.


The first line of treatment is behavioral and environmental interventions:

  • Don’t argue. It will only increase the person’s frustration. Imagine if you truly believe someone replaced your loved one and was lying about it. Would their arguing convince you?
  • Remind them that no matter who you are, you love them and are there to care for them.
  • Be patient as Capgras syndrome can cause real fear and anxiety.
  • Try distracting the person with an activity.
  • In some cases, a caregiver accused of being an impostor may be able to leave the room to get the “real” person, then come back in and no longer be perceived as an imposter.
  • Seek a medical evaluation to rule out conditions such as bladder infection, pain, constipation, and heartburn. These conditions are difficult for a person with dementia to communicate and can lead to worsening signs of dementia.
  • Limit exposure to the “imposter” when an episode is taking place.
  • Have the “imposter” speak before they are seen, as their voice may be recognized.

If behavioral interventions are not effective, medications may be called for.

  • Atypical antipsychotic medications, such as pimavanserin, quetiapine and clozapine, may be helpful.
  • People with AD may benefit from the antidepressant citalopram.
  • Individuals with Lewy body dementia may benefit from cholinesterase inhibitors, which block the breakdown of a neurotransmitter called acetylcholine.

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