Capgras syndrome is a psychological condition that is characterized by a belief that a particular person has been replaced by an impostor. This bizarre belief may lead one to acrimoniously accuse a friend or spouse of being “a fake” or an “impostor” of the actual person.
As you can imagine, Capgras syndrome causes great discord and anxiety in the lives of not only the person suffering from it, but also from the person being accused as well. This syndrome is sometimes called the “imposter syndrome” or “Capgras delusion.”
There is really no limit to what someone with this syndrome will accuse as being an impostor. In fact, according to Health Line, In some specific cases, someone who is experiencing Capgras syndrome may actually believe that an inanimate object, an animal, or even a home is an impostor. It has been shown that this syndrome can affect anyone. However, it’s more common in women, and in rare cases, it can affect children also. 
The exact cause of Capgras syndrome is unknown. However, research has helped to shed some light on some potential causes. According to Medical News Today, a common theory for the cause of Capgras syndrome is that it may be due to the result of a brain injury involving lesions on the brain.
According to the research, traumatic lesions on the brain were shown to be present in more than 1/3 of all documented cases of Capgras syndrome according to one study.  This sheds light to the possibility that there are many potential causes for Capgras Syndrome, as opposed to it being based on just family history and one’s environment alone.
Looking at further research, in a study of 38 subjects who suffered from Capgras syndrome, 81% of them had a neurodegenerative disease, most commonly Lewy body disease.
In fact, Capgras syndrome occurred at a younger age of onset in those who suffered from nonneurodegenerative disease simultaneously occurring with paranoid schizophrenia, schizoaffective disorder, and methamphetamine abuse and immediately after cerebrovascular events. Of the individuals suffering from Capgras syndrome and Lewy body disease, 100% of them experienced visual hallucinations compared with only one of those with Alzheimer’s disease (14%). 
In a study of 517 hospitalized, first-episode psychotic-disorder patients, researchers looked to see if any of them suffered from the symptoms of Capgras, as well as if there were any association with Capgras Syndrome and other mental illnesses such as major depression and bipolar-I disorder, among others.
Researchers found that Capgras syndrome was identified in 14.1% of patients. Their risk was at its greatest with acute or brief psychotic disorders (50%), brief (34.8%), or unspecified (23.9%) with psychoses, intermediate in major depression (15%), schizophrenia (11.4%) and delusional disorder (11.1%), and lowest in bipolar-I (10.3%) and schizoaffective disorders (8.2%). 
The symptoms of this syndrome are not as plentiful as most syndromes and mental diseases. Those suffering from this syndrome will believe a particular person to be an impostor or a “double” of another person.
They may become very fearful of the “impostor” or even become hostile and violent toward them. Irrational arguments can easily muster up between the one with the illness and the person whom they believe to be the “impostor” as they usually will accuse them of not being who they say they are.
This can be a very serious problem if they believe their spouse or parent to be an impostor. Capgras syndrome sometimes get’s confused with Fregoli syndrome. Though these syndromes are similar, they do have distinct differences. One of the biggest distinctions between these two common syndromes is that with Fregoli syndrome, there is a strong belief that other people are persecuting them.
Currently, there are no medications that are specifically designed to treat this illness. However, depending on the patient, there may be some indirect ways to help treat it. There may be some underlying causes to this syndrome.
For instance, someone who is also suffering from schizophrenia may find relief of their Capgras symptoms by taking antipsychotics. Medications that are used to treat dementia and Alzheimer’s disease may help as well (e.g. cholinesterase inhibitors). Surgery may also be a possible treatment method which would tend to brain lesions or head trauma. 
It has also been shown that risperidone and SSRI’s may be able to help as well. A study was done on an 11 year old Caucasian girl who had Capgras syndrome. After several subsequent follow-up evaluations with this patient, researchers were able to detect improvements in the psychotic symptoms following treatment with risperidone and selective serotonin reuptake inhibitors (SSRI’s), which suggests that this combined therapeutic approach may in fact significantly improve the actual clinical outcome in patients who suffer from Capgras syndrome. 
1) “What is Capgras Syndrome?” Health Line. https://www.healthline.com/health/capgras-syndrome
2) “What is Capgras Syndrome?” Medical News Today. https://www.medicalnewstoday.com/articles/320042.php
3) “Capgras syndrome and its relationship to neurodegenerative disease.” NCBI. https://www.ncbi.nlm.nih.gov/pubmed/18071040
4) “Capgras Syndrome in First-Episode Psychotic Disorders.” NCBI. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4065173/
5) “What is Capgras Syndrome?” Health Line. https://www.healthline.com/health/capgras-syndrome#treatment
6) “Clinical picture and treatment implication in a child with Capgras syndrome: a case report.” NCBI. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3520716/