Folie à deux and contagion

The best-known example of the social facet of paranoid behavior is the folie à deux, which, by definition, is an illness suffered by two. As this disorder is conceived, since it was described by Lasègue and Falret (3), a delusional system is shared by two people who almost always have a romantic or family relationship. It is worth noting that, although the number of cases published in the literature is small, when a researcher took the trouble to actively track the transmission of delusional ideas to the close ones of their paranoid patients, the frequency with which people in the immediate environment were also experiencing delusions was far higher than expected.

Hypochondriac delusional disorder.

"In my group of 50 patients, there are nine cases associated with folie à deux (or trois)" (4)

The two components of the delusional duo tend to maintain an asymmetric relationship, to isolate themselves from their surroundings, and to develop an unhealthy interdependence, forming a group strongly cohesive that, obviously, shares a set of paranoid beliefs…

Traditionally, the existence of an active inducer of the delusion and that of a passive recipient of it has been accepted. However, clinical observation shows that, at least on some occasions, it is both members of the pair who, influencing each other and acting in synchrony, develop, extend, and systematize the delusion. Thus, the delusion of the folie à deux presents itself to us as a social product, the product of a society, albeit one of very small size.

Folie à deux

"The mother also began to express doubts about her son's identity. She said that 'that boy' had been behaving irresponsibly by staying out late at night (as opposed to her son's true behavior). She examined old photographs of her son, discovering differences. Together, mother and daughter decided that the substitution of her son by a double must have occurred in 1983, when the 'bad behavior' first began" (1).

Subsequently, several cases would be described in which the delusional system is shared by several members of a family, which led to speaking of "folie à famille" or "shared psychotic disorder" (without specifying how many people, but admitting the possibility that there may be more than two).

On behavioral contagion

The vast majority of authors refer to the contagion of delusion as the core mechanism in the genesis of the disorder. A paranoid patient (the inducer, who plays a dominant role in the pair) would transmit to another person or persons, with whom they maintain a close relationship, their morbid idea.

Folie à six. The case of the Austrian hairdresser.

"She began to suspect the neighbors, fearing that they might start manipulating the family with technical devices. When she noticed that the electricity bill had gone up and one day saw an electrical cable hanging in front of her window, she felt this confirmed her suspicions. In the winter of 1984-1985 the delusion had engulfed the rest of the family. Her husband and two children had symptoms similar to hers during the night and fatigue in the morning. A sister-in-law and a nephew who agreed to sleep in the apartment also experienced uncertain physical symptoms" (2).

Contagion is a term applied primarily to infectious diseases, which are transmitted from individual to individual. Contact with a carrier (animal or human) places the recipient at risk of inoculating their own body with the pathogenic virus or bacteria, thereby contracting the disease.

Unlike what occurs in infectious diseases, it is argued that the maintenance of the delusion in the induced individual requires that the close relationship between the two individuals be preserved. Consequently, it is assumed that through simple separation, the delusion would remit only in that member of the delusional pair whose delusion is borrowed, but not in the ill "inducer." And this is indeed the case in the majority of instances, but not in all. There are delusional pairs in which, following physical separation, both individuals continue to have their delusions active — the presumed inducer and the presumed induced alike. Nor is the principle of asymmetry always upheld, as there are cases in which the relationship is relatively equal and neither of the two clearly gives the impression of being the dominant element of the pair.

Shared psychotic disorder is a true rara avis of Psychiatry, for in no other illness is the possibility of contagion admitted, except in one: hysteria. The classic descriptions of epidemic hysteric symptoms in the old large asylums are well known, but there is also historical evidence of epidemics that occurred in open contexts. Sirois (5) discusses the best-known of those outbreaks for which historical records exist since the Middle Ages.

The specialized literature continues to record the occasional occurrence of small epidemics of collective hystericism. GW Small et al (6) present a typical case: 247 adolescents, out of the 600 who were participating in a school recital, were affected by an acute condition that included the symptoms and characteristics typical of episodes of collective hysteria (at least those that have occurred and been published in recent times): rapid occurrence of a set of symptoms lacking any physical explanation, apparent transmission through sight or sound, preponderance in the female sex, presence of hyperventilation or syncope, preponderance in adolescents and preadolescents, rapid spread and remission of the condition, and evidence of an unusually stressful psychological situation.

Characteristic of these epidemics is their brief and self-limiting course. It should also be noted that what is transmitted in them is not only the phenomenon of conversion-dissociation but specific symptoms produced by that hypothetical mechanism. In other words, in hysterical epidemics each individual does not display their own conversion-dissociative symptoms but rather one specific symptom or set of symptoms, identical for all those affected.

Although for centuries the predominant symptoms appear to have been involuntary movements and sensory losses, Sirois (5) reports in his article that since the First World War the most frequent have been fainting, abdominal pain, nausea, headache, and hypotonia. Several reports published in the medical literature, such as that of Small (6), corroborate the episodic appearance of epidemic outbreaks with this pattern, especially in school settings.

These are episodes in which the predominance of somatic symptoms initially raises doubts regarding the possible toxic etiology of the condition, which sets in motion the emergency response mechanisms of the health authorities, facilitating both a medical and a psychiatric diagnosis. It is my view that in other contexts, primarily religious ones, episodes of collective hysteria continue to occur (visual hallucinations, states of trance and possession, etc.) more akin to the "older" kind, and that, however, since they do not generate the same alarm nor are interpreted as an illness, they go more unnoticed by Psychiatry.

Apparently, there are two major differences between hysterical epidemics and folie à deux:

the former have a brief duration while the latter is a disorder that can last for years or decades, if no therapeutic intervention occurs (and, in quite a few cases, even when it does)

it is thought that the contagion of folie à deux occurs as a consequence of an intense process of persuasion on the part of the patient toward the healthy member of the pair, whereas in hysterical epidemics no role is attributed to logical persuasion and the imitative and suggestive component appears to predominate.

The intriguing phenomenon of paranoid and hysterical contagion may perhaps seem less surprising if we consider that the contagion of behaviors is not limited to the realm of pathology but also occurs in some of the behaviors we consider healthy. To give two examples, sadness and laughter are two behavioral patterns that, as we all know, are transmitted with great ease from one individual to another. Much the same happens with impatience, anger, fear, or a smile.

This contagion of behaviors is not specific to our species either. Ethology teaches us that in social animal species (that is, in those that organize themselves into stable groups of individuals) some behavioral patterns — not all — have the potential to "spread" to the rest of the members of the group. The sudden onset of flight by a gazelle that has spotted an approaching predator triggers an equally swift flight on the part of the remaining members of the herd that have not seen it, the howl of a wolf prompts the rest of the pack to howl, and the reconciliation of two quarreling chimpanzees sets off among the group a jubilant clamor that seems to spread from one to another.