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Rare Capgras Syndrome Induced By Cannabis Drives Man To Attempted Murder


Dr. Katie Spalding

Katie has a PhD in maths, specializing in the intersection of dynamical systems and number theory.

Freelance Writer


Capgras Syndrome is a rare disorder that makes you believe those closest to you have been replaced by identical imposters. Image: fran_kie/Shutterstock

The 1978 movie Invasion of the Body Snatchers is a horror sci-fi about a bunch of aliens that come to Earth and slowly replace all the humans with identical copies. What makes the movie so scary is the paranoia – the characters’ knowledge that they can’t really trust anybody, even those they previously loved and trusted. For one 28-year-old man in Colombia last year, it came true – in his mind, at least.

“A 28-year-old male patient with no records of family psychiatric illnesses … was brought by the police to a psychiatric hospital due to an unsuccessful murder attempt against his neighbor,” notes the man’s case report, published in the journal Cureus.


“During the mental examination, it was evidenced that the patient believed their parents were killed some time ago, and impostors were now replacing them; therefore, he desired to murder ‘the impostors’.”

The man’s neighbors and parents had almost certainly not been replaced with pod people. The man in fact had a rare psychiatric disorder called Capgras syndrome. It’s only been recorded in around 250 people, with most occurring in people previously diagnosed with schizophrenia, dementia, or some other kind of neuropsychiatric condition.

However, the patient in the case report had no such illness. Instead, he was likely one of the tiny number of people whose Capgras Syndrome was brought on by cannabinoids.

“[Capgras Syndrome’s] relationship with recreational drugs represents an infrequent trigger described in only seven cases in the literature,” the case report explains.


“Therefore, it is mandatory to rule out first other organic and functional conditions that may trigger the disease.”

The doctors ordered a slew of tests, including an MRI brain scan and various STI screenings. Aside from one surprising result in the MRI – a “slight accentuation of cerebellar folia, which […] may represent a certain degree of cerebellum atrophy,” the authors explain – they all came back negative. That left only the patient’s eight-year cannabis habit as the likely explanation for his delusions.

While it may be characterized mainly by the belief that the people around you have been replaced with imposters, it’s usually not the only symptom of Capgras syndrome. The condition can manifest with paranoid delusions, dissociation, auditory or visual hallucinations, or other neuropsychiatric issues.

The patient in the case report had what the doctors describe as a “typical” case: he was “an aware patient, oriented to time, place, and person, seductive, with expansive mood, illogical thoughts, delusional ideas of the paranoid and megalomaniac spectrum, associated with poorly modulated affect, null introspection, and compromised judgment; no hallucinatory attitude manifested.”


“The patient identified himself as a famous musician and his grandfather as a renowned terrorist,” they note.

While trying to literally murder somebody may seem somewhat extreme, it’s actually not that uncommon for patients with Capgras Syndrome – “homicide” is listed as an associated symptom of the condition for one in twenty-five cases. And for those who study Capgras syndrome, it’s not difficult to understand why.

“It’s hard to imagine how distressing it would be to believe that someone you love has been replaced by a duplicitous double,” explained clinical and forensic psychologist Joni E. Johnston in Psychology Today. “Throw in the idea that this imposter has control over your mind, is plotting to take over the world, or has kidnapped your beloved and the only way to ‘free’ her is by killing her duplicate. In such a case violence can be a logical, albeit tragic, response.”

Luckily for all involved, this story does have a happy ending: after two months of treatment with a combination of antipsychotic and mood-stabilizing drugs, the patient’s symptoms completely cleared up. Meanwhile, the authors hope that the case’s unusual timeline, treatment, and likely cause will prompt further research into this mysterious – and no doubt distressing – condition.


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