[Folie à deux in schizophrenia--"psychogenesis" revisited].

Objective and method Since the 19th century, many studies have reported on folie a deux (FAD) in subjects with endogenous psychosis. However, the etiology of FAD in patients with schizophrenia has remained unclear, primarily because the possible psychogenic or reactive mechanisms of delusional contagion supposed in FAD were not compatible with the classical concept of endogenous psychosis. However, possible psychogenic mechanisms of FAD in schizophrenia were argued by Bleuler, E and Bleuler, M. The problem of how to distinguish the endogenesis from the psychogenesis (reaction) in FAD results in an aporia well-discussed in the German-speaking psychiatry: how induction in endogeneous psychosis might be possible? In the present study, first, a case of FAD in a husband and wife both with schizophrenia was reported. Three case reports of FAD in schizophrenic married couples from Japanese literature were also examined and the concept of the mind which lies in the background of psychogenesis/endogenesis dicotomy was discussed. Case report A 34-year-old housewife had constructed a persecutory delusion shortly after the death of her father. She became convinced that her relative who was a Yakuza (Japanese Mafia) member was planning to kill her. She also reported auditory hallucinations. Her 41-year-old husband, who had been diagnosed with schizophrenia six years before the incident, first denied the claim of his wife that she had become a target of the Yakuza. However, shortly after that, he came to be convinced that he had become a target of another Yakuza. The couple took refuge in the husband's parents' home. Nevertheless, each of them thought that only he or she would be assassinated and not his or her spouse. After hospitalization, the husband was separated from his wife and soon recovered from his delusional state. However, the wife partially kept her persecutory delusion and full insight into her mental disorder could not be obtained after treatment. According to Gralnick's definition and sub-classifications of FAD, this case was diagnosed as FAD, subtype of "folie induite". Discussions Observed delusions of folie a deux in schizophrenic couples were classified into the following two categories, based on the subjective pronoun of the delusional statement: 1) We-type: "We are persecuted", generally observed in cases of paranoid type schizophrenia, paranoid disorder, and shared paranoid disorder; 2) I-type: "I am persecuted", observed in cases of non-paranoid schizophrenia in particular. It could be argued that the We-type suggests the establishment of a delusional community within participants not seen in the I-type delusion. However, according to clinical observations, even in We-type delusion, subjects ignored the wills and thoughts of their partners and somehow constructed the delusional community in a somewhat one-sided and egocentric way. In both We-type and I-type delusional formation, true communication was not established because of the limitation to the solipsistic view point inherent to the subjects involved. Therefore, we designated the We-type delusional view point as Paranoid Solipsism in FAD and the I-type as Schizophrenic Solipsism in FAD. According to German traditional psychiatry, We-type Paranoid Solipsism may correspond to "psychogenic" delusional formation mechanism and I-type Schizophrenic Solipsism to "endogenous" mechanism. The structural similarity between Paranoid Solipsism and the Husserlian concept of transcendental ego was also discussed. The author suggested that classical "psychogenesis" theory in psychiatry was founded on the modern concept of mind, which is inseparable from the European philosophical tradition of self-concept by Descartes and Husserl. From the Japanese literature, the author pointed out that the majority of FAD cases in Japan took the form of possession psychosis until the 1970's, and that We-type and I-type delusional formation in FAD appeared only after the late 70's. The implication of these transformations of FAD phenomenology in accordance with social structure change was briefly discussed regarding the relationship between the modernity and FAD delusion.