Folie à deux: The shared psychosis

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Picture this: A couple has lived together for over 15 years. The husband has for the past 2 years, believed that their neighbor John is an FBI agent who has been spying on him and is trying to kill him. The wife, who has zero history of mental illness has recently reported that over the past 3 weeks, she too believes that John the neighbor is spying on her and is trying to harm her. 


Ok, what about this: 2 sisters who live together have a close relationship. For the past 3 years, sister 1 has believed that the sycamore tree in their backyard is infested with about 67 snakes, all which try to harm her whenever she steps foot in the backyard. As a result of this, she hasn’t been to the backyard in 3 years. Sister 2 who has no history of mental illness, didn’t believe this at first until 2 months ago when she reported that she could no longer go to the backyard as there were a lot of snakes on the sycamore tree trying to harm her. 

This condition is known as Folie à deux

What I find the most captivating about psychotic disorders, in general, is how they showcase the complexity and importance of the mind. It is just….. fascinating. 

Ok back to folie…

Folie à deux, also known as ‘induced psychosis’ or ‘shared psychotic disorder’ is a rare mental health condition, characterized by a delusional belief that is transmitted from one person who has a history of mental illness, to another who previously had no history of mental illness. This variation of psychosis usually involves 2 people who have a close relationship, live in close proximity to each other, and are relatively isolated from the outside world and other people. 


What typically happens here is that one person who has a psychotic disorder (usually schizophrenia) has a delusional belief which is later taken up by a close partner, relative or friend. The person with psychotic disorder is usually the dominant one in the relationship.

There is a variation of this condition where the delusional belief of one person is transmitted to a group of people who previously had no history of mental illness. This could happen in the scenario of a cult leader and cult members or followers.

This condition is fairly difficult to diagnose and treatment will usually involve separating the two parties, admitting them to a hospital, putting the recipient party through psychotherapy, and administering appropriate medications where necessary. 

Featured image: Healthland

Dr Wendy Evans-Uhegbu

The author Dr Wendy Evans-Uhegbu

Dr. Wendy Evans-Uhegbu is a graduate of The Royal College of Surgeons in Ireland, with experience in Connected Health, Medical Technology, Clinical Research, Medical Education, Medical Communications, and Web Design/Development. She is a part of the Medics Abroad team with the role of Chief Communications Officer. She is also a Medical Writer at 3D4 Medical and runs a Medical Communications and Children's books company (ODR Integrated Services/ ODR Books).  She is the author of the newly published children's book series "The Things Around Me".

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