Capgras Syndrome in Lewy Body Dementia

He May Think Your're an Imposter

Capgras Syndrome in Lewy Body Dementia
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Does your loved one with Lewy body dementia accuse you of being an impostor? He may have Capgras syndrome—a disorder first identified in 1989 that also goes by the names Capgras delusions, delusional misidentification syndrome, and the delusion of doubles. 

The Lewy Body Dementia Association describes Capgras syndrome as a "temporary but sometimes repeated belief that a caregiver, family member, or location has been replaced by an identical imposter." The most common subject of Capgras syndrome is the spouse or significant other.


Experts estimate that up to 17 percent of people with Lewy body dementia experience Capgras syndrome.

Hallucinations and Capgras Syndrome

Research indicates that hallucinations in Lewy body dementia are highly correlated with the development of Capgras syndrome. One study also found that people who were being treated with cholinesterase inhibitors (which are sometimes used to treat hallucinations in Lewy body dementia) were less likely to develop Capgras syndrome.

Prevalence of Capgras Syndrome in Alzheimer's

Research has concluded that there may be some people who have been diagnosed with Alzheimer's disease who also have developed Capgras syndrome, although some studies indicate they may also have some Lewy bodies in their brains.

Other Conditions Associated With Capgras Syndrome

Capgras syndrome has also developed in people with Parkinson's disease (which is very closely related to Lewy body dementia), schizophrenia, and drug abuse.

Capgras syndrome does not appear prevalent in people with frontotemporal dementia.

How to Respond

Caregivers of people with Capgras syndrome report increased challenges compared to caregivers of people with Lewy body dementia who do not display Capgras syndrome.

Because the cognitive function of people with Lewy body dementia varies greatly from time to time, responding to Capgras syndrome is difficult.

Sometimes, just going with the flow of the conversation will work, but some caregivers report that the person with Lewy body dementia will catch them in verbal inconsistencies if, for example, they agree that they're the imposter.

Additionally, since the person may believe the caregiver or family member is an imposter, verbal or physical aggression is possible, so caution is suggested in response to Capgras syndrome.

You may find that some of the same tips on responding to hallucinations in Lewy body dementia work well in Capgras syndrome since both hallucinations and Capgras syndrome are a misperception of reality.


Treating Capgras syndrome requires a cautious approach if medications are going to be used. People with Lewy body dementia are more at risk for serious side effects from antipsychotic medications which are often prescribed for paranoia, delusions and hallucinations. Be sure to report Capgras syndrome to your loved one's physician for proper evaluation and treatment.


Alzheimer's Disease and Associated Disorders. 2008 Apr-Jun;22(2):163-9. The prevalence of misidentification syndromes in neurodegenerative diseases.

Archives of Neurology. 2007 Dec;64(12):1762-6. Capgras syndrome and its relationship to neurodegenerative disease.

The Journal of Neuropsychiatry and Clinical Neurosciences 2008;20:494-494. A Possible Case of Capgras Syndrome After a Right Anterior Cerebral Artery Cerebrovascular Accident Treated Successfully With Mirtazapine.

Lewy Body Dementia Association. Capgras Syndrome in DLB Associated with Anxiety and Hallucinations.

Soonchunhyang Medical Science 17(2):72-74, December 2011. The Characteristics of Capgras Syndrome in Patients Diagnosed as Probable Alzheimer Disease.

International Psychogeriatrics. 2013 May;25(5):843-9. Capgras syndrome in Dementia with Lewy Bodies.

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