Folie a deux: Systematic review of the literature and presentation of a clinical case report

Introduction: Folie a deux is a rare disorder of much interest, because it suggests that a non-psychotic person can adopt and support ideas on the basis of relationship of dependence on a psychotic one. Folie a deux or induced delusiolar disorder, according to ICD-10 is characterized by the transference of delusional ideas, usually persecutory type, from one person, so called inducer, to another, the recipient. Sometimes, more than one individuals are affected by the inducer. Folie a deux is considered to be rare but it is possible that many cases go unercognized. It is generally proposed that the inducer is dominant, forceful personality, older than the recipient, of higher intelligence and better education. Most commonly he or she suffers from schizophrenia or paranoid disorder. the pair had been living together in close intimacy for many years , usually socially isolated, and this deprivation of external stimuli is believed to play a critical role in the development of the disorder. Psychodynamic aspects suggest that the acceptance of the delusional ideas by the recipient is been carried via identification with the inducer. In the majority of cases the involving persons are members of a family. The most common combinations to Western countries are two sisters, husband and wife and parent-child.

With respect to the treatment, separation of the involved individuals is considered to be of limited effectiveness, particularly when the recipient is an adult.

Case report: Mrs M, a 51-years old female was committed to our clinic from a local hospital and she was accompanied by her 48-years old sister, Mrs. H. Both sisters had been hospitalized involuntary in a psychiatric institution, one month ago. The sisters were living in a small village the last ten years, with their mother. According to Mrs. H, their problems started right after they moved from a big city back to the village because as she claimed their neighbours poisoned her sister by putting drugs in the milk and eggs they brought them with the etiology that the two sisters were aware of a conspiracy against one of their cousins. She also reported that when they tried to contact with lawyers the police blocked the phone and the post mail. Their relatives confirmed that the two sisters and their mother lived under conditions of poverty and social isolation. Mrs. M had expressed delusional ideas and Mrs. H adopted them. Mrs H revealed that her sister had a hearing problem. Mrs. M was described as more intelligent and stronger character than Mrs. H, as the leader of the family. Laboratory tests revealed anemia and the otological examination, with thw performance of an audiogram, detected otosclerosis which had caused her significant hearing loss. the diagnosis for Mrs. M was delusional disorder, persecutory type, and for Mrs. H induced delusional disorder, according to ICD-10. the date for re-examination was fixed for a month later, but they didnít show up.

Discussion:The research on folie a deux has been focused on the features of the recipient that make someone vulnerable to the induction of the delusional ideas of the inducer. A number of characteristics had been described, included submissive and dependent personality, physical disability and sensory impairment. These factors are been considered to increase someoneís dependency, resulting in the acceptance of the induced ideas. Furthermore, low intelligence of the recipient is been believed contributing to the genesis of folie a deux as well as other conditions which impair cognitive abilities, impairing reality testing, thus resulting in the development of the disorder.

What differentiates our case from the majority of the reported cases is:

  1. It was not the recipient but the inducer who suffered from physical disability (anemia) and sensory impairment (otosclerosis) and
  2. The recipient was of normal intelligence and of better education than the inducer.

Despite the theories and views about the concept, every case of folie a deux is unique: each one of the involved persons requires specific clinical assessment, not only for the estimation of mental state but for the determination of physical disability as well. Clinicians should bear in mind that it may be the inducer suffering from an organic disease and ask for examination and laboratory tests for both the involved persons. Appropriate treatment of co-morbid conditions may improve the prognosis of this hard to manage disorder.

Key words: Induced delusional disorder, folie a deux, inducer, recipient, delusional ideas.