One man's “Cat-gras” delusion suggests our understanding of the underlying syndrome may be flawed.
Capgras syndrome is a disorder wherein a person believes someone close to them—a family member, friend, loved one—has been replaced by an imposter. To the person with the delusion, the "imposter" looks and sounds just like their loved one, but something about them just seems off.
Capgras delusions are observed most often in patients with psychiatric disorders like schizophrenia, though they're also found in people with dementia or brain injuries.
In a new study published recently in Neurocase, doctors discuss a 71-year-old male with an interesting case of Capgras—or "Cat-gras," as they're calling it, because the patient was convinced his pet cat had been replaced by an imposter.
It's rare for patients with Capgras to have delusions about animals rather than humans, although it has only been documented a handful of times. Two cases with cats, two with pet birds, and one with a pet dog have been reported, and in all of these cases, the patients were largely socially isolated with little to no close human interaction.
"Oftentimes, in the other cases that were described it was someone who was older and living alone and so it may have been that their pet was really the most important and strongest connection that they had," said Ryan Darby, an author of the study and a clinical neuroscience fellow at the Berenson-Allen Center for Noninvasive Brain Stimulation in Boston.
The paranoia caused him to stop taking his medication, and it was then that the patient started to believe his pet cat had been replaced by an imposter cat
This patient, however, was not socially isolated. He was married and frequently interacted with friends and family. So, his "Cat-gras" delusions weren't a result of a lack of human interaction. They also weren't a result of a psychotic break like many of the other cases were. Instead, it's likely his Capgras stemmed from a series of head injuries incurred when he was younger.
"He had been a semiprofessional hockey player and had sustained some mild concussions," says Darby, "and then he had fallen more severely about 30 years before we saw him, which caused a bleed, a subdural hemorrhage, on the right side of his brain. We could see a scar from that on his brain."
Symptoms of these head injuries started to appear well before his Capgras delusions, according to Darby. He was forced to retire after becoming aggressive with his co-workers and a bipolar diagnosis followed shortly after. Then came years of manic episodes like the time he spent $40,000 in one month and when he started hoarding magazines and electronics. He also had episodes of social withdrawal and became frequently forgetful. Later came the paranoia. He became convinced that strangers were FBI agents and started writing notes to his wife instead of speaking when he began to suspect their house was being monitored. The paranoia caused him to stop taking his medication and it was then that the patient started to believe his pet cat had been replaced by an imposter cat that was in on the conspiracy against him.
According to Darby, "In some cases you can reason with Capgras patients and they say they know it sounds crazy. Sometimes in the moment you can get them to admit that they know it's probably not true but then you ask them five or ten minutes later and it's such an engrained belief at that point that it's really hard to reason through."
"Once you accept that initial experience as being true and valid then it's hard to break that belief," says Darby. "If you've had a debate with someone who's really engrained in their political beliefs, it's really hard to sway them even if you have a lot of good reasons. I think it's often the same case in patients like this."
The "Cat-gras" went away once the patient resumed his medication, but this particular case led Darby to reformulate the current ideas on what's happening in the brain to cause these delusions.
"The more popular theories that came out initially in the 1990s were related to face perception and the disconnect between being able to recognize someone as being the same person from our memory and the emotional experience that happens when we see something familiar—the thing that gives us that personal connection to it," he said. "More to our case, the fact that it was involving a pet cat really moves away from the face processing idea and more towards something a little bit more general."
Instead, Darby believes the problem may lie with the inability to retrieve autobiographical memories, or memories of personal experiences, particularly ones relating to the supposed "imposter." Because they can't connect any personal memories to the "imposter," it becomes hard for the Capgras patient to believe that their loved one or pet is really them.
"This is an interesting case," says Darby, and it's one that has pushed him to study Capgras more in other patients. Thats where his theory will really be tested. With each new case comes an opportunity to further validate or refute this new idea. So, in the name of science, call Ryan Darby if an imposter has suddenly replaced your family member or loved one. Or your cat.