A functional psychotic reaction in which two persons who have long been intimately associated come to share the same delusions.The first hospital case was reported in 1860, and the name was suggested by Ernest Charles Lasegue and Jean Pierre Falret in 1877. The dominant member of the pair develops paranoid delusions, usually of a persecutory nature, and talks so much and so persuasively about his false ideas that they come to be accepted by the more dependent, submissive, and suggestiblm member. The transfer of delusions from one to the other is due largely to the fact that they are both poorly adjusted individuals who live together in comparative seclusion, have a narrow range of interests, and face the same stresses. In some cases there is evidence that the closeness of relationship stems not only from a similarity in pre-psy- chotic personality but also from an unconscious homosexual bond.One study of over a hundred cases revealed the following combinations: two sisters, 40; husband and wife, 26; mother and child, 24; two brothers, 11; brother and sister, 6; father and child, 2. The investigator, Gralnick (1942), attributed the greater incidence among women to the fact that in our society they are more frequently required to play a passive role and have a narrower range of interests and activities than men. The fact that such a large proportion of patients were husband and wife would seem to rule out hereditary or constitutional factors. If the two individuals are separated and independently treated, the more dependent member of the pair tends to abandon his delusions sooner than the more dominant one who provoked them.Illustrative Case: FOLIE A DEUX The daughter was twenty-eight years old and the mother sixty-five at the time of their admission to a mental hospital from the women's jail of a large city in Canada. Both they and the girl’s father had been bom abroad and had come to Canada when the daughter was a child. They were quite poor and neither the mother nor daughter had much education. Six months before their admission to the hospital, the father was admitted to an old people’s home. Even before this, the mother and daughter had worked, eaten, and slept together for many years.On arrival at the hospital, the daughter stated that six years previously she had developed a nasal obstruction and a plastic surgeon in the United States had performed an operation on her nose. Soon after, shewas involved in an automobile accident on her way to the doctor’s office and was thrown against the windshield of the car. She complained that ever since she suffered from excruciating pains in her nose, face, and neck. She had attempted to sue the doctor for half a million dollars but no lawyer would take the case. Subsequently, she and her mother entered the doctor’s house and refused to leave until he paid. They were arrested, jailed and deported to Canada. On five occasions after this the two entered the United States and attempted to sue the doctor. Finally, the United States immigration officer in Canada refused to issue visas to them. They decided that the doctor was paying the immigration officer to keep them out of the United States and therefore tried to collect the half million dollars from the immigration officer. For several weeks they waited in his office every day until they were arrested and taken to jail from which they were transferred to the hospital.In addition to her primary delusions, the daughter reported that she and her mother had a great deal of trouble in rooming houses during the preceding months because other people were after their money. The mother told exactly the same story as the daughter and felt that all of the daughter’s claims were well founded. She was very anxious for the daughter to marry and looked forward to living with her and the hypothetical son-in-law, but she believed that it would be impossible for the girl to find a husband unless her nose was healed. Both wished to be released as soon as possible in order to return to the United States and collect their money from the doctor.Shortly after admission, they were separated from each other for three months while the daughter underwent an intensive program of ECT and insulin coma treatment. Initially, her delusional system changed and she began to believe that the doctor wished to pay her the half million dollars but was being prevented from doing so by her relatives. Soon, however, she reverted to her former beliefs and thereafter these remained unshakable. During the period of separation, the mother first became severely depressed and then, as often happens with separation in folie a deux, lost her faith in the daughter’s delusional system. Nevertheless, she could not accept the fact that her daughter was ill and remained anxious for the two of them to leave the hospital. When treatment of the daughter was terminated as useless, she was reunited with her mother and they remained inseparable companions in a chronic ward of the hospital. (Rosen and Gregory, 1965)

Cite this page: N., Pam M.S., "FOLIE A. DEUX," in, November 28, 2018, (accessed February 17, 2019).