Folie à deux

This is about the mental disorder, the studio album is at Folie à Deux (album)

Folie à deux (FaD) is a type of mental illness. It is also called induced delusional disorder or shared psychotic disorder. It is a rare condition where two or more people in a close relationship share a specific delusion.[1]

The name folie à deux means "madness of two" in French. While most cases occur between two people, the condition can occur among three people (folie à trois), four people (folie à quatre), within an entire family[2] (folie en famille), or in a large group (folie à plusieurs).[3]

Jules Baillarger first reported the condition in 1860.[1] Ernest-Charles Lasègue and Jules Falret named it folie à deux in an 1877 article.[4]

Characteristics

In FaD, delusional beliefs are transferred from a psychotic person (called the primary, principal, or inducer) to another person (called the secondary, acceptor, or associate).[5] The secondary person comes to believe that the primary person's delusions are real. The secondary person adopts those delusions; now both the primary and the secondary share the delusion. (This is why FaD is also called "shared psychotic disorder.")

Prevalence

FaD generally develops between people who have lived together for a long time and are attached to each other.[5] It usually occurs among family members, though there have been cases involving friends, families, physicians and patients, and even a dog.[5]

In a study of all FaD cases reported between 1993-2005, almost all (98%) occurred within the nuclear family.[6] Over half (52%) occurred between married or long-term couples. Another quarter (24%) occurred between sisters.[6] Another study found that around 50% of cases occur either between sisters, or between mother and daughter.[7]

Primary & secondary

In many cases, there was already a difference in power between the primary and secondary even before FaD developed.[8] In some cases - but not all - the secondary partner is younger than the primary partner, more passive, less intelligent, more trusting, and/or has lower self-esteem.[9]

Proposed types

In an important 1942 article, psychiatrist Alexander Gralnick listed four types of folie à deux. Each type involves the transfer of delusional beliefs from one person to another.[10]

Folie imposée

Folie imposée means "imposed madness." In this type of shared psychosis, a person forms a delusion and passes it on to someone else (who might be younger and more submissive).[5] If that secondary partner separates themselves from the psychotic person, their delusions usually disappear quickly.[3] In Gralnick's study of 103 cases of folie à deux, almost 60% were the imposed type.[10]

Folie communiquée

Folie communiquée (communicated psychosis) is similar to folie imposee. In both types, a person forms a delusion and passes it on to the secondary partner. However, in folie communiquée, the secondary partner resists the delusion for a long period before finally adopting it. Even if they are separated from the psychotic person, their delusions continue.

In Gralnick's study of 103 cases of folie à deux, the communicated type was the second most common form of the disorder (with 24 cases).[10]

Folie simultanée

Folie simultanée means "simultaneous madness." This condition involves two people who are already psychotic and have their own separate delusions. They influence each other, and their delusions become very similar.

Folie induite

In folie induite (induced psychosis), both the inducer and the secondary partner already have psychosis, and the secondary partner develops the inducer's specific delusions.

Criticism

Newer studies seem to indicate that this classification may not be sufficient to fully describe folie à deux.[6] Critics say there may be more symptoms than are usually described in the cases above. Also, in many cases, separating the two patients may not be enough to make the condition go away in one of them. Also, the person described as "sane" before developing the folie à deux may already be suffering from a psychiatric illness, or may develop one.

References

  1. ↑ 1.0 1.1 Al Saif, Feras; Al Khalili, Yasir (2025), "Shared Psychotic Disorder", StatPearls, Treasure Island (FL): StatPearls Publishing, PMID 31095356, retrieved 2025-09-14
  2. ↑ Erol A, Ersoy B, Gulpek D, Mete L. Folie à family: case report. Anatolian J Psychiatry. 2008;9:261–264.
  3. ↑ 3.0 3.1 Enoch, David; Puri, Basant K.; Ball, Hadrian (2020-11-23). Uncommon Psychiatric Syndromes. Routledge. ISBN 978-1-4987-8796-3.
  4. ↑ Lasègue, C; Falret, J. La folie à deux. Ann Med Psychol. 1877;18:321–355.
  5. ↑ 5.0 5.1 5.2 5.3 Cipriani, Gabriele; Abdel-Gawad, Noha; Danti, Sabrina; Di Fiorino, Mario (November 2018). "A Contagious Disorder: Folie à Deux and Dementia". American Journal of Alzheimer's Disease and Other Dementias. 33 (7): 415–422. doi:10.1177/1533317518772060. ISSN 1938-2731. PMC 10852512. PMID 29772920.
  6. ↑ 6.0 6.1 6.2 Arnone D, Patel A, Tan GM. (2006). "The nosological significance of Folie à Deux: a review of the literature". Ann Gen Psychiatry. 5 (11): 11. doi:10.1186/1744-859X-5-11. PMC 1559622. PMID 16895601.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  7. ↑ Mouchet-Mages S, Gourevitch R, Lôo H. Folie à deux: actualités d’un concept ancien, à propos de deux cas. Encephale. 2008;34(1):31–37.
  8. ↑ Vargas Alves Nunes A, Odebrecht Vargas Nunes S, Strano T, et al. Folie à Deux and its interaction with early life stress: a case report. J Med Case Rep. 2016;10(1):339.
  9. ↑ Rahman T, Grellner KA, Harry B, et al. Infanticide in a case of folie à deux. Am J Psychiatry. 2013;170(10):1110–1102.
  10. ↑ 10.0 10.1 10.2 Gralnick, A. (1942). Folie à deux—the psychosis of association; a review of 103 cases and the entire English literature, with case presentations. Psychiatric Quarterly, 16, 230–263. https://doi.org/10.1007/BF01576134
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