What Is… Folie à Deux (Shared Psychotic Disorder)

characteristics of folie à deux (shared psychotic disorder)

In this series, I dig a little deeper into the meaning of psychology-related terms. This week’s term is shared psychotic disorder, also known as folie à deux.

Folie à deux is the more commonly recognized name for what the DSM-5 calls shared psychotic disorder. It’s a rare condition that involves shared delusions between two or more people who are in a close relationship. The primary, or inducer, in the relationship holds the original delusional belief, and then the secondary, or induced, in the relationship comes to share the delusion.

How it develops

The disorder was first identified in the late 1800s. In 1942, psychiatrist Alexander Gralnick proposed four subtypes of folie à deux based on how the shared delusions came about:

  • folie imposée (imposed psychosis): the primary imposes the delusional beliefs on the secondary
  • folie simultanée (simultaneous): both people were psychotic to begin with, and came to share a delusion
  • folie communiquée (communicated): the “normal” secondary maintains the delusion after separation
  • folie induite (induced): a psychotic person adds new delusions to another psychotic person’s delusional system

Risk factors

Several risk factors contribute to the development of folie à deux, including:

  • lengthy relationship with strong attachment, usually family members
  • social isolation
  • personality disorders: histrionic | dependent | schizoid, schizotypal
  • personality traits: neurotic, emotionally immature, passivity, suggestibility, suspiciousness
  • untreated mental illness in the primary in the relationship; most common diagnosis is delusional disorder
  • cognitive impairment in the secondary
  • stressful life events
  • communication difficulties
  • female gender

Cases of folie à deux

More than half of reported cases involve either mother-daughter or sister-sister pairs. The primary plays a dominant role, while the secondary plays a submissive role. In some cases, the entire family becomes involved; an 11-member family suicide reported in India was suspected to be due to shared psychosis.

There was a fascinating case report in the Archives of Sexual Behaviour that described a married couple involving a female primary and male secondary. The shared delusional belief was that the husband was being financially exploited by a mistress (whom he worked with) and was being given drugs and forced to have sex with her. While he did not have memories of events his wife described, he was entirely certain that they occurred and didn’t question any of it.


In terms of treatment, perhaps the biggest challenge is getting the pair (or system) to accept the need for treatment. The atypical antipsychotics aripiprazole and quetiapine appear to be most effective for medication treatment. It helps to separate the person or people with the secondary disorder from the person with the primary disorder, as the secondary’s delusions often don’t persist following separation. One would guess that you’d need to throw a lifetime of therapy into the mix as well.

Folie à millions

In his 1955 book The Sane Society, psychologist and philosopher Erich Fromm described folie à millions as a social pathology of normalcy. Essentially, this involves socially-induced mass insanity.

In a 2021 interview with Scientific American, psychiatrist Brandy X. Lee used the term folie à millions to describe President Donald Trump’s influence over his supporters. She states, “When a highly symptomatic individual is placed in an influential position, the person’s symptoms can spread through the population through emotional bonds, heightening existing pathologies and inducing delusions, paranoia and propensity for violence—even in previously healthy individuals. The treatment is removal of exposure.”

While I have many issues with Donald Trump and those who say “how high?” when he says “jump”, I personally don’t think it’s helpful to frame that as psychosis. Similarly, I don’t think what happened with Hitler in Nazi Germany is the same phenomenon as what happens on an individual-to-individual level in shared psychotic disorder.

Paging Dr. Freud

Shared psychotic disorder sounds like a bit of a Freudian wet dream. In psychoanalytic theory, unresolved Oedipus/Electra complex issues leading to jealousy or abnormal sexualization of the relationship are thought to contribute to the development of folie à deux.

I vaguely recall when I worked in inpatient psychiatry there was one patient that was part of a suspected folie à deux, but I’ve never encountered a clear-cut case.

It’s fascinating the things the mind can do.

You can find the rest of the what is… series in the Psychology Corner.


  • Al-Saif, F., & Al Khalili, Y. (2022). Shared psychotic disorder. StatPearls.
  • Harris, N. (2019). Recovering the critical potential of social pathology diagnosis. European Journal of Social Theory22(1), 45-62.
  • Jolfaei, A. G., Isfahani, M. N., & Bidaki, R. (2011). Folie à deux and delusional disorder by proxy in a family. Journal of Research in Medical Sciences: The Official Journal of Isfahan University of Medical Sciences, 16(Suppl1), S453.
  • Lew-Starowicz, M. (2012). Shared psychotic disorder with sexual delusions. Archives of Sexual Behavior41(6), 1515-1520.
  • Lewis, T. (2021). The ‘shared psychosis’ of Donald Trump and his loyalists. Scientific American.
  • Sharon, I. (2018). Shared psychotic disorder. Medscape.
  • Tamminga, C. (2022). Shared psychosis. Merck Manual Professional Version.
  • Wikipedia: Folie à deux

The post Let’s Talk About Psychosis is the hub for all psychosis-related content on Mental Health @ Home.

Book cover: Making Sense of Psychiatric Diagnosis by Ashley L. Peterson

Making Sense of Psychiatric Diagnosis aims to cut through the misunderstanding and stigma, drawing on the DSM-5 diagnostic criteria and guest narratives to present mental illness as it really is.

It’s available on Amazon and Google Play.

Ashley L. Peterson headshot

Ashley L. Peterson


Ashley is a former mental health nurse and pharmacist and the author of four books.

28 thoughts on “What Is… Folie à Deux (Shared Psychotic Disorder)”

    1. Shared psychotic disorder would only be possible if the person originating the belief was psychotic. And I’m not familiar with the people you mentioned, but I think in the case of cultish leaders the leader is twisted and probably narcissistic, but not psychotic. I suspect if they were psychotic, they wouldn’t have been in any condition to be able to manipulate and brainwash others.

        1. Huh, just looking at an article on the American Psychological Association’s website, and from their description it doesn’t sound like he was psychotic. They described him as being very aware of what he was doing, and he borrowed a lot of techniques from George Orwell’s 1984 to deliberately control his followers.

          1. Hmm? I’ve seen documentaries on David Korache and Jim Jones, and they were both considered narcissist psychotic. Oh, they were aware of wht they were doing, but what they had done by twisting the minds of their followers was undeniably horrific.
            Jim Jones of Jones Town was famous back in 1978. That’s where the saying of “Don’t drink the Koolaide” comes from.

            1. I know this might sound very twisted, but I find true life crime stories very interesting. I don’t glorify what they have done, but more along the lines of how they had fit into society for as long as they did, undetected.
              Ted Bundy, for one… Freaked the hell out of me. The BTK Killer, the list goes on and on.
              I think my interest came from my father being a detective for most of his career.
              The inner thinkings of killers truly fascinate me.
              I would love to hear your view on the following. 🤔

            2. Yeah, I love watching those kind of shows on Netflix. They’re so highly skilled at doing such atrocious things – it’s fascinating (although not in a good way),.

  1. I’ve witnessed this illness in a family where a mother is very psychotic and her two adult children. The daughter was receiving treatment was managing relatively supporting her mother who was very unwell. This definitely impacted the daughter’s own mental health. Unfortunately, the son also became very psychotic. It was really heartbreaking to witness. I just had strong empathy for the father who had to handle all these people if they all became unwell at the same time. We just have to thank God for our blessing.


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