Folie à Deux: A Delusion Shared by Two
Got a delusion, can you share it? Yes, two can share a delusion... if one of them is mad.
The madness of two
Folie à deux refers to the transference of a delusion from one person to another. The term was coined in 19th-century France, with the first documented case involving a married couple convinced strangers were breaking into their home and wearing down their shoes. (Happens to me all the time; someone’s also been drinking all my milk.)
“Doctor, doctor, please help me, I’m plagued day and night by tiny alligators. They crawl all over me!” says the patient, flicking away imaginary reptiles.
“Well, good God, man! Don’t get them on me!” yelps his psychiatrist.
A shared delusion is typically no laughing matter. The burden appears to be no lighter for being shared, causing great distress to its sufferers and sometimes even resulting in violent lashing out. A real-life case of folie à deux was the inspiration for the film Heavenly Creatures, wherein two girls murder one of their mothers in a misguided bid to remain together, largely in a fantasy world of their making.
These days folie à deux is known as shared psychotic disorder and can refer to more than two people sharing the same delusion. The five-day paranoia-fueled road trip of the Tromp family is a recent example. Three adult children were involved, two of whom were swept up in their parents’ bizarre beliefs, and one who went along to keep an eye on everyone else. The family was thought to be missing during this time, being uncontactable by design. After they were found, thankfully unharmed, police concluded that the danger which drove them from their home was merely imagined, then propagated from parent to child and blown out of all proportion in the process.
Mass hysteria or mass psychogenic illness is a different kettle of fish. In the case of mass delusion, suggestibility and social contagion are the culprits behind a frenzied crowd, rather than any underlying predilection toward psychosis. Plainly put, the perfectly ordinary person is susceptible to the sort of ‘catching’ anxiety that leads one to stock their trolley with enough toilet paper to last the year after observing another shopper do the same.
Double trouble: risk factors for folie à deux
A primary or inducer, with any number of possible psychiatric conditions, transfers a delusion to one other, known as a secondary or an associate. Folie à deux becomes a closed feedback loop, with each person reinforcing and amplifying the other’s delusional beliefs.
Shared delusions are of the persecutory or grandiose sort, as are most delusions, whether the subject of a hallucination or a dream. Sufferers believe they are at the mercy of malevolent forces or vengeful folk, or else that they possess superior (and often supernatural) abilities. Sometimes the two types of delusions are combined such that a person is convinced they are uniquely endowed with the ability to see the hostile entities that plague us all.
Primaries most commonly suffer delusional disorders, followed by schizophrenia, and affective disorders such as depression. In times past, it was thought that the secondary was merely the conduit of transferred delusional ideas, psychologically normal prior to the onset of folie à deux. This is far from the truth.
Secondaries are also predisposed to psychosis, with exposure to someone else’s delusion acting as a trigger rather than being the underlying cause. Many secondaries manifest delusions other than folie à deux, with between 29–89% diagnosed with a comorbidity such as schizophrenia, depression, cognitive impairment, or bipolar affective disorder.
The vast majority (98%) of folie à deux cases occur within the nuclear family, with secondaries frequently the offspring of the primary. Sisters and common-law couples are the next most common pairing after parent-child dyads. Passivity, low self-esteem and intelligence, and in particular, being caged by social isolation, are risk factors for the secondary becoming ensnared in the dominant person’s delusion.
Case study
A nine-year-old boy with a family history of psychiatric illness is abused and neglected. His suffering precipitates early-onset psychosis in the form of folie à deux, leading to horrifying hallucinations shared with the closest thing he has to a caregiver: his grandmother.
These visions often took the shape of bloody human beings: one was black, one was a baby, and some could change shape (get fatter or thinner, or become larger or smaller). The hallucinations were perceived as a meeting but our patient was unable to understand the language spoken. At the end of this meeting, one of the characters would tell him that he should kill himself. He was convinced that they were talking about him and sending him a special message. Our patient reported sleep deprivation due to these hallucinations. — Link
Isolation and dependence on this one maternal figure, this rock out at sea, results in a close bond between grandson and grandmother. Thus, the child reflects her hallucinations and delusions of prosecution by otherworldly forces, in no small part because of the love and attention he receives. Unfortunately, closeness comes at the price of his increasing distress.
In this case, the grandmother is the “real” psychotic, a person who is believed to have a respectable position within the family due to her “super power”, which grows in strength as more people believe her visions. — Link
Trading sanity for sympathy?
Parallels can be drawn between somatic symptom disorders where a patient subconsciously feigns or exaggerates an illness and folie à deux. Both psychiatric conditions fulfil an emotional need, one for succour, the other for intimacy, although the nature of the symptoms—a feigned physical rather than a mental disorder—differs.