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The Cult Dossier · No. 171 · Shared Psychosis / Mandated Killing

Folie à Deux

Shared psychotic disorder; induced delusional disorder; madness shared by two

1877 – present · France originally; the diagnosis is used worldwide

XVII. SHARED PSYCHOSIS AND THE MANDATE TO KILL

Not religious in itself, though the shared delusion frequently is. Where two isolated people share a religious conviction nobody else can check, this is the clinical description of what is happening.

Who led it

Named in 1877 by the French physicians CHARLES LASÈGUE (1816-1883) and JULES FALRET (1824-1902), in a paper titled LA FOLIE À DEUX OU FOLIE COMMUNIQUÉE.

What it worshipped and taught

A delusion held by one person is adopted by another in close relationship with them. The clinical structure is consistent: A PRIMARY, or INDUCER, who is genuinely psychotic and usually dominant; a SECONDARY, or INDUCED, who is not independently psychotic and is usually dependent; and SOCIAL ISOLATION, without which it does not occur. THE BELIEF CANNOT BE CHECKED BECAUSE THERE IS NOBODY LEFT TO CHECK IT AGAINST.

Who was in it

Lasègue and Falret; the compilers of the DSM and ICD; the pairs in 172, 173 and 174.

How it ended, or where it stands

STILL OBSERVED, STILL RARE, AND NO LONGER ITS OWN DIAGNOSIS. It survives as a description rather than a category.

The dead

—

Of note

FOLIE À DEUX IS THE SMALLEST POSSIBLE CULT, AND THAT IS WHY IT IS IN THIS FILE.

Take everything the groups in this dossier rely on and reduce it to the minimum workable size. One person supplies reality. Another accepts it. Contact with anyone who might contradict it is cut. The belief becomes unfalsifiable not because it is clever but because THE ONLY AVAILABLE WITNESS AGREES. That is a two-person version of Jonestown, of the Solar Temple, of every compound in era IX, and it requires no charisma, no doctrine and no money.

THE CLINICAL FINDING THAT MATTERS MOST TO THE REST OF THIS DOSSIER IS THE TREATMENT. Separate the secondary from the primary and the secondary often improves. THAT IS A REAL, DOCUMENTED EFFECT, THOUGH NOT A RELIABLE ONE — separation alone can fail or make things worse — and it is almost certainly the true observation that the deprogrammers of entry 150 generalised into something false. Removal can work, for an induced delusion in a dependent person in a two-person isolate. IT IS NOT EVIDENCE THAT SEIZING AN ADULT OFF THE STREET REVERSES A RELIGIOUS CONVERSION, and the courts were right to say so.

NOTE ALSO WHAT SEPARATION DOES NOT FIX. The primary stays ill. In every case in this era, the person who generated the delusion was not cured by being taken away from the person who adopted it. APPLIED TO THE GROUPS IN THIS FILE, THAT IS THE ARGUMENT FOR PROSECUTING LEADERS AND TREATING FOLLOWERS, which is roughly what modern practice has arrived at by a completely different route.

A CORRECTION, RECORDED HERE RATHER THAN AT THE TOP BECAUSE IT CHANGES A NAME AND NOT THE ARGUMENT. THIS ENTRY PREVIOUSLY NAMED JEAN-PIERRE FALRET AS LASÈGUE’S CO-AUTHOR AND THAT WAS WRONG. The 1877 paper was written with JULES FALRET (1824-1902), who was Jean-Pierre’s SON. Jean-Pierre Falret (1794-1870) is a real and important psychiatrist - he described folie circulaire, the condition now called bipolar disorder - but he had been dead seven years when this paper appeared. THE TWO MEN ARE CONFUSED CONSTANTLY IN SECONDARY SOURCES, and L291 exists so that this file cannot quietly make the mistake twice.

Its timeline

  1. 1860 JULES BAILLARGER reports the phenomenon. The name comes seventeen years later.
  2. SEPTEMBER 1877 LASÈGUE AND JULES FALRET publish LA FOLIE À DEUX OU FOLIE COMMUNIQUÉE in the ARCHIVES GÉNÉRALES DE MÉDECINE.
  3. 20th century The concept is extended to folie à trois, à quatre and à famille — whole households sharing one person's delusion.
  4. DSM-IV Formalised as SHARED PSYCHOTIC DISORDER.
  5. DSM-5 (2013) REMOVED AS A SEPARATE DIAGNOSIS. Cases meeting the criteria are now recorded as delusional disorder, or otherwise under other specified schizophrenia spectrum and other psychotic disorders. ICD lists it as INDUCED DELUSIONAL DISORDER. The phenomenon did not go anywhere; the classification of it changed.
  6. Present THE FIRST STEP IN TREATMENT IS SEPARATION. Removed from the primary, the secondary tends to improve faster than the primary does. IT IS NOT RELIABLE: current clinical reviews warn that separation by itself can be insufficient or can make the condition worse, and antipsychotic treatment is commonly needed as well.

Its people

Charles Lasègue

Ernest-Charles Lasègue

French physician; co-named folie à deux · 1816 – 1883 · active 1877

A Parisian physician who came to medicine from philosophy, and who left his name on several unrelated things — a sign of sciatic nerve irritation, one of the first clinical descriptions of anorexia nervosa, and, with JULES FALRET, the 1877 paper LA FOLIE À DEUX OU FOLIE COMMUNIQUÉE. That paper did something the psychiatry of its day rarely bothered to do: it described a delusion as a thing that MOVES BETWEEN TWO PEOPLE rather than as a fault inside one skull, and it specified the conditions under which the transfer happens.

Before the law. None.

Where things stand. Deceased. HIS PAPER IS STILL THE DESCRIPTION EVERYONE USES, a hundred and fifty years on, even though the diagnosis itself was removed from the DSM in 2013. The three conditions he and Falret set out — a dominant primary, a dependent secondary and social isolation — have not needed amending.

  1. 1816 Born in Paris.
  2. 1873 Publishes on what is now called anorexia nervosa, independently of Gull in London.
  3. SEPTEMBER 1877 With JULES FALRET, publishes LA FOLIE À DEUX OU FOLIE COMMUNIQUÉE in the ARCHIVES GÉNÉRALES DE MÉDECINE.
  4. 1883 Dies.

Checked 2026-09-06

Jules Falret

Jules Philippe Joseph Falret

French psychiatrist; co-named folie à deux · 1824 – 1902 · active 1877

The son of JEAN-PIERRE FALRET (1794–1870), who had described folie circulaire, the alternating condition now called bipolar disorder. Jules worked at the Salpêtrière and co-wrote the 1877 folie à deux paper with Lasègue. HE IS ROUTINELY CONFUSED WITH HIS FATHER, including by sources that ought to know better and including, until this file was corrected, by entry 171. Jean-Pierre had been dead seven years when the paper appeared.

Before the law. None.

Where things stand. Deceased. THIS FILE INCLUDES HIM SEPARATELY FOR ONE REASON: to make the father-and-son confusion hard to repeat. If a source says Jean-Pierre Falret co-wrote the 1877 paper, that source has not checked, and whatever else it says should be read in that light.

  1. 1824 Born, into a family already central to French psychiatry.
  2. 1850s–1870s Works at the Salpêtrière; publishes on delusional states.
  3. SEPTEMBER 1877 Co-publishes LA FOLIE À DEUX OU FOLIE COMMUNIQUÉE.
  4. 1902 Dies.

Checked 2026-09-06

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