What is… Folie à deux

Mental Health @ Home Insights into psychology: folie a deux

In this series, I dig a little deeper into the meaning of psychology-related terms.  This week’s term: folie à deux

Folie à deux is the more commonly recognized name for what’s known as shared psychotic disorder in the DSM-5.  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 has the original delusional belief, and then the secondary, or induced, in the relationship comes to share the belief.

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 delusions became shared:

  • 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 for the development of folie à deux include:

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

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, and 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.  Aripiprazole and quetiapine appear to be most effective for medication treatment.  One would guess that a lifetime of therapy would need to be thrown into the mix as well.

This condition sounds like a bit of a Freudian wet dream.  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 my What Is series here.



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27 thoughts on “What is… Folie à deux

  1. Meg says:

    Wow, I love quirky, weird stuff like Munchausen’s, and now this one! Weirdness!!

    I’d never researched the condition, so your blog post was very informative. I might have misunderstood the concept prior to now. I’d thought it was when two people came together and committed horrific acts (killing, etc.) that they wouldn’t have done on their own, having not met the other person. One fascinating case of that involves murder mystery writer Anne Perry. I used to read all her Charlotte and Thomas Pitt novels. In real life, when she was a tween, she and her best friend conspired to kill the best friend’s mother, and they did. They accosted the mother in the park and beat her to death with heavy stones, and it wound up taking longer and being harder work than they’d thought to end her life. They both did time in juvie and were released upon condition that neither ever contact the other during the rest of their lifetimes, for any reason, and they’ve held to it.

    Hmm…. the way you describe it makes me think of cults, but I know that’s deliberate mind gaming, whereas this condition sounds more like shared beliefs without any intentional brainwashing (i.e., the “cult leader” would genuinely believe what he’s forcing, rather than doing it for money or fame, or whatever).

    So fascinating! Great blog post!! I love talking and thinking about this weird psych stuff!!

    • ashleyleia says:

      Oh that’s interesting about Anne Perry.

      i suspect with cults that the leaders they’re twisted but not psychotic; if they were psychotic they probably wouldn’t be in a state of mind to manipulate and brainwash others.

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