Folie à Deux

/ Lasègue-Falret syndrome, folie imposé /


This kind of shared psychosis is a psychiatric syndrome in which symptoms of a delusional belief and sometimes hallucinations are transmitted from one individual to another. The disorder was first conceptualized in 19th-century French psychiatry by Charles Lasègue and Jean-Pierre Falret and is also known as Lasègue-Falret syndrome. The term is from French for madness by two – Folie à Deux. It was described as folie communiqué in 1860 by Jules Baillarger and as folie à deux in 1877 by Lasegue and Farlet.

Many synonyms have been used for describing this condition, which mainly reflect the idea of the condition’s transmissibility, viz. ”communicated insanity”, ”contagious insanity”, ”infectious insanity”, ”psychosis of association” and ”double insanity”.

A rare delusional disorder shared by two or, occasionally, more people with close emotional ties. Also, literature reveals cases of folie à trois, folie à quatre, or even folie à famille (family madness) and even a case involving a family dog. Folie à plusieurs (madness of several). In the most recent update to the Diagnostic and Statistical Manual of Mental Disorders (DSM-5), shared psychotic disorder was removed as a separate disease entity and was included in the section on other specified schizoprenic spectrum and other psychotic disorders. The majority of patients with folie à deux require multiple treatments including separation, antipsychotics, individual and group psychotherapy and family therapy. It is most commonly diagnosed when the two or more individuals concerned live in proximity and may be socially or physically isolated and have little interaction with other people.

Various sub-classifications of folie à deux have been proposed to describe how the delusional belief comes to be held by more than one person:

FOLIE IMPOSÉE is where a dominant person initially forms a delusional belief during a psychotic episode and imposes it on another person or persons with the assumption that the secondary person might not have become deluded if left to his or her own devices. If the parties are admitted to hospital separately, then the delusions in the person with the induced beliefs usually resolve without the need of medication.

FOLIE SIMULTANÉE describes either the situation where two people considered to suffer independently from psychosis influence the content of each other’s delusions so they become identical or strikingly similar, or one in which two people “morbidly predisposed” to delusional psychosis mutually trigger symptoms in each other.

Also, when a large number of people may come to believe obviously false and potentially distressing things based purely on hearsay, these beliefs are not considered to be clinical delusions by the psychiatric profession and are labelled instead as mass hysteria.


There are 4 main types of delusions that are passed on from an inducer to a secondary person:

bizarre delusions

non-bizarre delusions

mood-congruent delusions

mood-neutral delusions


Bizarre delusions are clearly implausible and not understood by peers within the same culture, even those with psychological disorders; for example, if one thought that all of their organs had been taken out and replaced by someone else’s while they were asleep without leaving any scar and without their waking up. Not only is it impossible for someone to survive having all their organs taken out and replaced, but if they did survive they would be covered in scars, would be in a crippling amount of pain and would not be able to move.

Non-bizarre delusions are common among those with personality disorders and are understood by people within the same culture. For example, if one thinks that the FBI is following them in unmarked cars and watching them via security cameras, they are having a non-bizarre delusion. While this is highly unlikely for the average person, it is possible and therefore understood by those around them.

Mood-congruent delusions correspond to a person’s emotions at the time, usually during an episode of mania or depression. For example, someone with this type of delusion may believe that they are going to win $2 million at the casino tonight, despite the fact that the majority of people who go to a casino walk away having lost money or in some cases leave with some money, but rarely over $100 and almost never $2 million. Similarly, someone in a depressive state may believe that their mother will get hit by lightning the next day, despite the fact that only about 240,000 people are injured by lightning strikes per year (out of a global population of approximately 7.57 billion as of 2019).

Mood-neutral delusions are the opposite of mood-congruent delusions as they are unaffected by mood, and can be bizarre or non-bizarre; the formal definition provided by Mental Health Daily is “a false belief that isn’t directly related to the person’s emotional state.” An example would be if one were steadily convinced that somebody had switched bodies with their neighbor, as the belief remains independent of whether they may be in a manic or depressive state.

Therefore, folie à deux is undoubtedly an intriguing condition of great relevance to the understanding of human psychopathology. It is perhaps the most impressive example of a pathological relationship and, therefore, an understanding of its underlying mechanism has theoretical implications for other kinds of disturbed interpersonal relationships.


Notable cases

I The mother, a 40-year-old divorcee from a low socioeconomic background, with primary school education presented with continuous illness of 8 years’ duration interspersed with exacerbations and partial remissions. She accused her neighbours of plotting to do away with her and her son by poisoning their source of drinking water. She also charged them with having used witchcraft and black magic to kill them. She was often found verbally abusing the neighbours at the top of her voice. She stopped visiting them and actively resisted any social calls by them. She even forced her son to stay indoors and cut off all links with their neighbours. She soon included her own family members in this conspirational network when she saw them with the neighbours on a number of occasions.

A mental state examination on the day of admission revealed an unkempt and agitated lady clinging to her son. The rapport was poor and her responses were brief and evasive. She also had persecutory delusions, an anxious mood and third person auditory hallucinations. She was admitted to the hospital and after a detailed evaluation was diagnosed to have paranoid schizophrenia.

Physical examination and preliminary investigations were within normal limits.


II In May 2008, in the case of twin sisters Ursula and Sabina Eriksson,Ursula ran into the path of an oncoming articulated lorry, sustaining severe injuries. Sabina then immediately duplicated her twin’s actions by stepping into the path of an oncoming car; both sisters survived the incident with severe but non-life-threatening injuries. It was later claimed that Sabina Eriksson was a ‘secondary’ sufferer of folie à deux, influenced by the presence or perceived presence of her twin sister, Ursula – the ‘primary’.

Sabina later told an officer at the police station:

We say in Sweden that an accident rarely comes alone. Usually at least one more follows – maybe two.

However, upon her release from hospital, Sabina behaved erratically before stabbing a man to death.


III It was suspected a family of eleven members from Burari, India suffered from this condition. On 30 June 2018, the family committed suicide due to the shared belief of one of its members.


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