Folie à Deux – Shared Psychotic Disorder

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Folie à deux is a shared psychotic disorder where the delusion is shared between two individuals.

Criteria for a folie à deux as described by Dewhurst and Todd:

  • definite evidence that the partners had been in intimate association
  • a high degree of commonality in the content of delusion, although the formal psychosis may differ
  • unequivocal evidence that the partners share support, and accept each other’s delusions

In the DSM -5 it is included under the section on psychotic disorders and does not exist as a separate entity.

There are four subtypes: (Gralnick, 1942)

  1. Folie imposée – Delusional belief of a psychotic person is imposed on another person or persons.
  2. Folie simultanée – The simultaneous development of an identical delusion between two individuals with psychosis who may be closely associated
  3. Folie communiquée – A normal person suffers from a delusional belief of a psychotic person after resisting it for a long time and then maintains it despite the separation.
  4. Folie induite – A person who is already psychotic adds new delusions from another closely associated individual with psychosis.