What Happens When Three People Share A Delusion and Commit Crimes As a Result? – A Case Report of Folie à Trois

Folie à Trois, J Marley, Public Domain

I recently came across an unusual case of Folie à Trois (via @drjezphillips) described by Joshi and colleagues in the December 2006 edition of the Journal of the American Academy of Psychiatry and the Law. Folie à Trois occurs when one person has a delusion (a fixed, false and unshakeable belief which may appear bizarre and usually falls into one of several types) which is then shared by two other people. A variation on this is Folie à Deux which as the name suggests involves a shared delusion between two people. Folie à Deux is uncommon enough but cases of Folie à Trois are very rare*. The authors of this paper have used material from the public domain as source material for the report but were also involved as examiners in the court case.

The case involved three sisters. Prior to this episode the sisters did not have a history of mental illness although there was a family history of Schizophrenia in their mother and brother.  The youngest sister had developed insomnia, left college and become social withdrawn. Her two sisters were living next door and supporting her. The second oldest sister had three children. However all three sisters started to spend increasing periods of time with each other and became increasingly isolated from other people.

The youngest sister then developed the delusion that a certain house that she had wanted to live in was indeed hers. This belief was then shared by the two sisters. All three sisters dressed in their pyjamas proceeded to get in the car, along with the second sister’s three children and drive to the house. The youngest sister knocked at the front door and asked the person who answered the door if her room had been prepared. The person in the house quickly closed the door. The youngest sister tried to gain entry into the house through the window. Meanwhile the police arrived. At this point the situation deteriorated further and the two olde sisters decided that they wanted to seriously harm the police officer. They proceeded to attack the police officer.

All three sisters were arrested and put in a police cell whilst social services took  the children into their custody. In the police cell the sisters developed paranoid delusions about the police officers. Again they attacked the police officers who escalated their response by using Mace spray. Despite this the sister continued to attack the police officers.

The treatment revealed the subtle nature of Folie à Trois. The youngest sister was admitted to a psychiatric unit, diagnosed with Schizophrenia and treated with an antipsychotic medication.

Without any need for psychiatric intervention, once the two older sisters were separated from their younger sibling their delusions resolved.

The authors have written a review of the literature which includes a reference to Gralnick’s four delusion subtypes (folie imposée, folie simultanée, folie communiquée and folie induite). The characteristics of the relationship between those sharing the delusion may be important (dominance of the person who initially develops the delusion) but the literature review suggests that simple generalisations about these relationships are not always reliably found in Folie à Trois.


* At the time of writing, a search on Medline retrieved 17 papers on Folie à Trois and 198 papers on Folie à Deux

Index: There are indices for the TAWOP site here and here Twitter: You can follow ‘The Amazing World of Psychiatry’ Twitter by clicking on this link. Podcast: You can listen to this post on Odiogo by clicking on this link (there may be a small delay between publishing of the blog article and the availability of the podcast). It is available for a limited period. TAWOP Channel: You can follow the TAWOP Channel on YouTube by clicking on this link. Responses: If you have any comments, you can leave them below or alternatively e-mail justinmarley17@yahoo.co.uk. Disclaimer: The comments made here represent the opinions of the author and do not represent the profession or any body/organisation. The comments made here are not meant as a source of medical advice and those seeking medical advice are advised to consult with their own doctor. The author is not responsible for the contents of any external sites that are linked to in this blog.

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