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Induced delusional disorder: a case report of Folie A' Famille

Case Report

Induced delusional disorder (or shared paranoid disorder), also known as folie a' deux, is a relatively rare disorder typically characterized by the presence of similar psychotic symptoms in two or more individuals. However, the number of reports on delusions shared by more than two people is extremely small. Folie a' famille is a form of the psychopathological condition known as folie a' deux, where all the members of a family share the same delusions. Usually the "primary" case", i.e. the individual who first develops psychotic symptoms, can be distinguished from one or more "secondary" cases, in whom the symptoms are induced. The etiological studies of folie a" deux are grouped under two headings: i) genetically transmitted-structural factors; and ii) environmental-psychological factors.

The case history, clinical and diagnostic issues, and treatment of a family sharing the same delusion are presented. There were four members in the family: father, mother, two sisters. All four cases fulfilled modern operational definitions for induced delusional disorder in that: i) the partners were intimately associated, ii) they had identical delusional content, iii) there was an acceptance and support of the delusional ideas by all four members. The case history of all family members, as well as an extensive clinical examination of them, led to the conclusion that the youngest daughter was the "primary" case and the rest of them the "secondary" cases, even though the mother had long ago developed a paranoid personality disorder. At the age of twenty-four the youngest daughter while studying at the university far away from her family began to present atypical somatic symptoms, paranoid ideation with ideas of reference and delusions of persecution. Soon after she moved back home, it became clear that both parents and the sister also developed the same delusional symptoms.

The whole family abandoned their house and their jobs and started a purposeless roaming far away from their town in order to escape form their "persecutors". During this face, the family was involuntary admitted to the Psychiatric Hospital. The four persons were separated in four different psychiatric departments of the same hospital. Later, they were transferred to psychiatric clinics of four different towns. At that point an improvement of the father and the eldest sister was observed. An early discharge of the "primary" case gave them the opportunity to re-organise the whole paranoid system.

The whole cycle with involuntary admissions to the Psychiatric Hospital started again. During this phase (for various reasons) only the mother and the eldest sister received anti-psychotic medication. Furthermore, the separation of the family in different hospitals, although it is undoubtedly the appropriate therapeutic intervention, cannot be achieved at present due to bureaucratic reasons.


It has been argued that the only "non-genetic" factors in the aetiology of schizophrenia are stochastic events affecting gene expression or structure. Therefore, shared or induced delusional disorders, folie a' deux and especially folie a famille, provide unique opportunities to consider the relative roles of genetic and environmental risk factors in the aetiology of psychotic illnesses.


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Open Access This article is published under license to BioMed Central Ltd. This is an Open Access article is distributed under the terms of the Creative Commons Attribution 2.0 International License (, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Katsigiannopoylos, K., Pazarlis, P., Zambioglou, G. et al. Induced delusional disorder: a case report of Folie A' Famille. Ann Gen Psychiatry 5 (Suppl 1), S276 (2006).

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