Shared Psychotic Disorder (SPD), also known as Induced Delusional Disorder (IDD) or Folie à deux is a psychiatric condition shared by two or more people with close emotional links and characterized by transfer of delusional aspects from one primary affected person (the inducer, the primary or the dominant partner), who first develops psychotic symptoms or is suffering from an already established psychotic disorder (most commonly believed to be schizophrenia), to one or more secondaries (the inductee or the recipient), in whom the symptoms are induced.
First described by French Lasègue and Falret (1877) as Folie à deux, or insanity of the two, the same syndrome shared by more than two people and depending on the number three, four or in some cases the whole family is called Folie à trois, Folie à quatre and Folie en famille, or family madness, respectively. Their study assumed some etiological factors that notably shaped the rationale and psychological thought behind SPD with little supporting evidence or critical examinations (Armone D, Patel A, & Tan GM, 2006). Further studies of different cases involving SPD resulted in different variants being added to its original description but it was in 1942 that an effective definition of SPD was presented with all of its variants included in distinguished four subtypes: subtype A or folie impose: the inducer imposes his or her delusions on a younger and more submissive person. Both people are intimately associated, and delusions of the recipient disappear after separation; subtype B or folie simultanée: the simultaneous appearance of an identical psychosis occurs in two intimately associated and morbidly predisposed individuals; subtype C or folie communiquée: the recipient develops psychosis after a long period of resistance and maintains symptoms even after sepertaion; and subtype D or folie induite: new delusions are adopted by individual with psychosis who is under the influence of another individual with psychosis (Gralnick A, 1942). Standardising, Folie à deux is classified in Diagnostic and Statistical Manual of Mental Disorders as “shared psychotic disorder” (DSM- IV – TR, 2000) and International Classification of Diseases as “induced delusional disorder” (ICD – 10, 1992). The diagnosis in both the classification systems in based in phenomenology rather than etiology.
Diagnostic Consideration
Diagnostic criteria for SPD includes that a delusion should develop in an individual in the context of a close relationship with another person, who already has an established delusion, the delusion is similar in content to that of a person who already has the said delusion and the delusion is not better accounted for by another psychotic disorder.
SPD often is difficult to diagnose as people suffering from this syndrome do not regard themselves as mentally ill due to lack of insight and often oppose psychiatric help(Manschrek T, 2000). SPD also causes diagnostic problems as sometimes it can be hard to tell a difference from an already established psychosis, especially while diagnosing individuals with same ancestry (Dippel B, Kemper J & Berger M, 1991). The major psychosis in the inducer was believed to be schizophrenia but it is now evidently clear that variety of other mental illness can also be responsible for this disorder (Armone D etc al., 2006) thus making shared psychotic disorder accurately uncommon, but not as rare as it was thought to be.
Literature review
This study focuses on two major literature reviews done on SPD, one by Silveria and Seeman (1995), who studied extensive case reports from 1942-1993 and the second by Armone, Patel and Tan (2006) which extended and updated on the former, and studied case reports from 1993-2005. The studies provide some contrasting differences in terms of Demographic characteristics, family and psychiatric history, the nature of the relationship, risk factors, duration of the association and the exposure, diagnosis, co-morbidity and psychopathology. We compare the significant and statistically significant factors which will give us more insight in making a strong point in our hypothesis.
The difference between mean age of the primaries and secondaries during 1942-1993 (48.1 and 42.9 years) and during 1993-2005 (52.7 and 45.9 years) is not statistically significant. The
difference in gender was also not statistically significant when it came to secondaries but for primaries Silveria and Seeman(1955) recorded an excess of women (18 men and 43 women as compared to 13 mean and 28 women during the case study from 1993 onwards).
The majority of relationships between the primaries and the secondaries during 1993-2005 were within the nuclear family (97.6%). The largest portion among them were couples (52.4%) followed by relationship between sisters (23.8% out of which 50% were twins). Compare this to the results found in cases between 1942-1993, the majority relationships were within the family but the dyad parent-child contributed more significantly (31.1%) followed by siblings (sisters) and couples (29.5%).
Cognitive, emotional and social attributes contribute to the risk factors for the development of SPD. Social Isolation has been found to be the major risk factor. Social isolation was reported in 64.3% of the cases during 1993-2005 and 84% during 1942 -1993. Cognitive impairment, life events were other major factors reported in the secondaries. The duration of association between primary and secondary was found to be longer during 1993-2005 suggesting longer interaction between primary and secondary.
The commonest diagnosis in primary was delusional disorder followed by schizophrenia during 1993-2005 but in cases during 1942-1993 the order of frequency was different with schizophrenia first followed by mood and delusional disorders. In secondary, SPD was the primary diagnosis (71% during 1993-2005, 88.5% during 1942-1993) but other disorders were also highly represented.
Data from 1993-2005 shows comorbidity among secondaries is higher (Armone D etc al., 2006). Their study supports the possibility that close proximity or primary and secondary only constitute a temporal trigger for a psychiatric condition in already susceptible individuals. Presence of family psychiatric history suggests a similarity in genetic loading for psychiatric disorders between primary and secondary. The common belief that separation as the means of treatment of secondary(Silveira JM & Seeman MV, 1995), although which sounds logical by the very definition of SPD, is the only sufficient intervention required is not supported. Secondaries were treated with medication similar to the primaries, and in conjunction with separation and psychotherapy, revealing that separation is not always the treatment of choice. This can be explained as secondaries themselves develop other psychotic disorders and the separation doesn’t help, so a broader definition is required which can compass all these cases as well. Although schizophrenia is very common, delusional and affective disorders were also commonly seen, implying that the inclusion criteria should be widened to include more cases, further, hallucinations which are not included in diagnostic occur frequently and therefore should be included in the classification system as well.
Conclusion
SPD forms part of the spectrum of psychotic disorders, it is still poorly understood in practically every aspect of its nature, including etiology, phenomenology, treatment and prognosis.
Although uncommon because the definition and the diagnostic criteria are not as inclusive as they should be, as the studies suggest (Arome D etc al., 2006), they are not as rare as previously thought. Many cases of SPD remain hidden as individual with this condition may experience a little impairment, they generally remain outside hospital settings. While many individuals with SPD seek assistance from other medical specialists, they are increasingly being recognized as psychiatrically ill (Manschrek T, 2000). The data shows that primary need not only have schizophrenia to induce shared psychotic symptoms in the secondary, but that other mental disorders could also be responsible. The shared psychotic symptoms themselves need not only be delusions but can also be hallucinations, similarly the default treatment of separation is shown to be inadequate or insufficient in most cases. This shows that this phenomenon can occur very well out of the scope of current definition and diagnostic standards, and as such is not rare as it was thought to be.