East Asian Arch Psychiatry 2017;27:121-4


Folie à deux by Proxy in a Father, after Physical Abuse by a Mentally Ill Daughter
JL Tay, Z Li

Ms Jing-Ling Tay, MSc, RN, Institute of Mental Health, Buangkok Green Medical Park, 10 Buangkok View, Singapore 539747.
Ms Ziqiang Li, BSc (Nursing), RMN, RN, Institute of Mental Health, Buangkok Green Medical Park, 10 Buangkok View, Singapore 539747.

Address for correspondence: Ms Jing-Ling Tay, Institute of Mental Health, Buangkok Green Medical Park, 10 Buangkok View, Singapore 539747.
Tel: (65) 6389 2344; Fax (65) 6389 2465; Email: jing_ling_tay@imh.com.sg

Submitted: 9 June 2016; Accepted: 23 May 2017

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This is the first case report in a country predominated by Chinese that describes the physical abuse of a recipient by the inducer in shared delusional disorder. The report describes a 42-year-old patient who physically abused her father until he submitted to her delusions. Subsequently and for years, both sustained persecutory delusions against their neighbours. While the patient was undergoing treatment, the father continued reinforcing her delusions. There is a need to explore the possibility of any forms of abuse of the recipient by the inducer in shared psychotic disorder. This report discusses the development of such delusions in a specific case and makes recommendations for the management of similar cases.

Key words: Father-child relations; Shared paranoid disorder


Folie à deux, or induced delusional disorder, refers to the transference of delusions from the primary person (inducer) to a secondary person (recipient). It occurs most commonly within nuclear families, as both persons in the family live within close proximity to each other,1 which is convenient for the sharing of thoughts and feeling. This is the first case report that describes the physical abuse by the inducer of the shared delusion of the recipient until he succumbed to similar delusions. This case report also describes a minority race and offers relevant recommendations for practice.

Case Report

A 42-year-old female patient presented to our institution for admission, accompanied by police in 2015. She had been arrested for continually shouting at passers-by and pouring milk outside her neighbours’ houses. She belonged to the minority race of Indian, in a country whose population is predominantly Chinese. A corroborative history was provided by the patient’s second sister.

Social Situation

The patient was the youngest child in the family. Her mother had passed away more than 2 decades ago. A few years later, her second sister married and moved out of their home. The patient had been staying with her father and the adopted and intellectually disabled eldest sister for about 20 years. The 90-year-old father was the main breadwinner and carer. At home, he prepared all meals for the whole family.

Among the 3 siblings, the second sister was the only one who had received a formal education and the only one who was employed and married. The patient and her eldest sister had never attended any school; neither had they engaged in any proper social life. The patient had never left her neighbourhood. The patient helped her father with domestic chores but had never been engaged in any formal employment.

The Mother

Despite not being formally evaluated, the mother had been noted to have unusual behaviour. She had abhorred family gatherings and was estranged from her own siblings. She was often seen talking to herself and slept poorly. She was seen scolding her neighbours and throwing rubbish into their houses. The father had never interfered with her actions. He would apologise to the neighbours after each aggressive episode by the mother. The father dissuaded the mother of her beliefs and was resolute that they were untrue.

The mother had also developed suspicions about her daughters. Since then, she had never spoken with them and had refused to consume any meal they prepared. On her deathbed, she had refused to see her daughters. The patient was just 3 years old when her mother passed away.

The Patient, the Father, and the Other Sister

For about 15 years, a few years after the second sister was married and moved out of their family home, the patient became symptomatic. She believed that her neighbours were following her. She consequently developed conflicts with several neighbours. She followed the neighbours and secretly took photos of them. She refused to take the same elevator with them and was often seen leaving the elevator whenever other neighbours entered. She also took photos of police and police cars, accusing them of deliberately following her. She believed that they were discriminating against her because of her race (minority). She also believed that they looked down on her as she was uneducated and could not speak English. At home, she often hid in her room, talking, laughing, mumbling, and cursing. Later she became suspicious of and hostile towards her second sister and forbade other relatives to visit.

Initially, the father and the second sister attempted to stop the patient’s behaviour. Nonetheless on a few occasions when the father confronted and scolded her for following neighbours, she attacked her father using hands and cane, until he was defenceless and fell to the ground. Over the years, the father gradually developed the same beliefs. The father eventually concurred with the patient and encouraged her to seek help from the authorities to stop the neighbours’ harassments. The father also ignored the second sister’s pleas to bring the patient for professional help. Instead, he told her not to interfere. He firmly believed in the patient and refused to listen to anyone else. The physical abuse of the father ceased completely.

The mildly intellectually disabled adopted eldest sister nonetheless never directly refuted her sister. For years, the eldest sister locked herself in her own room whenever the patient verbalised paranoid thoughts to the family.

After the last 5 years of shared delusion, and acting to protect themselves, the patient and father covered all the windows with towels and paper. The family home, like its occupants within, looked as if it was attempting to hide from the community.


While the patient was being confined for treatment, the father continued to receive instructions from her, for example, to put litter into neighbours’ houses. He bargained with the treating team for her discharge and disagreed with the treatment recommended. The treating team eventually had to restrict the father’s visits to the patient to once per week as he was hampering her treatment. With the help of the second sister, the patient was commenced on antipsychotic therapy. Over 5 months of hospitalisation, her condition gradually improved. On discharge, community support was organised including visits by psychiatric community nurses and support by social workers from family service centres.


Case Summary

The history of psychosis began with the mother. Decades after the mother’s death, the youngest daughter of the family, with the most dominant personality, developed psychotic symptoms. She was physically aggressive to the father when he denied her delusional claims, and eventually, the father developed delusional disorder by proxy.

Literature review indicates that shared delusional disorder most often occurs among married couples, siblings, and mother and child.2 In this case, folie à deux occurred between the father and daughter, which is uncommon.

Causative Factors

The patient’s mother experienced auditory hallucinations and paranoid delusions. She likely had schizophrenia but was never diagnosed formally nor treated. A positive family history of mental health problems is a prominent causative factor among inducers. Although the adopted eldest daughter stayed with the patient, she was not genetically predisposed to psychosis. Similarly, the second sister, despite her genetic loading, escaped the diagnosis as she did not live in close proximity to the patient.

Social isolation is also a huge risk factor.1 The second sister probably escaped the delusional disorder as she was educated, had friends, and married. On the contrary, the patient never had any friends. She could only travel within her neighbourhood and was isolated in her own home. To complicate matters, she could only speak her native language. As she belonged to a minority race, communication with the majority of the public was almost impossible. The patient was essentially disconnected from public life and reality. This disconnection caused her to be increasingly distrustful, hostile and irritable, contributing to her psychopathology.3

The patient remained with the father and was emotionally close to him. Psychodynamic theory views this closeness as a double-edged sword.3 The submissive father accepted the patient’s delusions rather than risk jeopardising their relationship. The disruption of ego development is another causative factor.3 Electra complex states that young girls are required to identify with their mother in order to develop their sexual identity and life role. In this case, the patient’s mother passed away when she was 3 years old, removing any opportunity for the patient to identify with her. As a result, the patient misidentified with her father, leading to an inappropriate bonding between them. Psychodynamic theories also describe the role of an ambivalent relationship in shared delusional disorder. The father and the patient were very dependent on each other. The father cooked for the whole family and was the main source of social support for her and provided with her a ‘job’. The patient did not work. She instead helped the father with domestic chores. Despite this apparent dependency on the father, the patient was the inducer. For many years, she was reliant on the father for many things. On the contrary, the father’s life purpose, meaning for life and self-esteem were dependent on her. When the patient developed paranoid delusions, the father initially drew away from her. As a result, their loving relationship abruptly became one based on hate and the patient resorted to violence towards her father.

The father was subjected to physical abuse (as a form of negative reinforcement) whenever he opposed the patient’s delusions. Behaviourist theory endorses the role of classical conditioning that resulted in the father being the eventual recipient. Learning theory supports the view that the father eventually learned to adopt the delusions from the more domineering patient.

Abuse and Psychiatric Disorders

People with schizophrenia or other psychoses are at increased risk of being violent and even homicidal.4

This is especially true for those who experience positive symptoms.5 In another case of shared delusional disorder, a mother had bipolar disorder and was non-compliant with treatment. She did not let her daughter go to school and subjected her to physical abuse. The daughter eventually succumbed to the mother’s belief that people were attempting to kill or electrocute them.6 Therefore, shared delusional disorder may be dangerous for the recipient. In this case, the father persistently resisted his wife’s delusions for many years, and never succumbed to it. His wife was never physically abusive. Conversely, the patient physically abused and coerced her father until he concurred with her paranoid delusions. The father was 75 years old when the patient became delusional and abusive. After years of abuse, agreeing with his daughter’s delusions was probably the only way to survive with his fragile health. Although the father was never seriously injured, he still sustained delusional disorder by proxy.

The association between any forms of child abuse and psychiatric disorders has been established.7 Nonetheless there is limited research into the association between mental health problems and physical abuse of adults. There is a need to conduct more research about the correlation of abuse in adults with mental health problems, especially in shared delusional disorder.

Treatment of Shared Delusional Disorder

There are 4 subtypes of shared delusional disorder.8 In folie imposée, delusions are transferred to a sane recipient. Folie simultanée occurs spontaneously in 2 premorbid predisposed and intimate individuals. Folie communiqué happens when the recipient initially resists the delusions but then adopts the same delusions and continues to do so even after separation. Folie induite happens in 2 individuals already with psychosis. The recipient adopts new delusions from the inducer. Separation is recommended for all 4 types of folie à deux, although it works best for folie imposée.9

Pharmacological management and electroconvulsive therapy are recommended for the inducer. Non-pharmacological management such as psychotherapy and family therapy are useful for both inducer and recipient.1

During the patient’s hospitalisation, the father visited daily and reinforced her delusional beliefs. Hence, the treating team decided to restrict his visits to weekly. After discharge, community social workers and psychiatric nurses worked with the patient and her father to help them integrate back into the society.

Recommendations for Practice

There is a need for public education about the promotion and enhancement of mental health needs. The public needs to be more informed about mental health disorders. This will reduce stigmatisation, promote early illness discovery, treatment, and overall recovery.10

Worldwide globalisation has resulted in increased numbers of immigrants. These minority immigrants have a 3-fold increased risk of mental health disorders.11

Community centres or services should organise more activities to strengthen community cohesiveness, especially among minority groups. There must be opportunities to allow people of different races and nationalities to interact with one another. There should also be complimentary language classes to facilitate social integration and prevent social isolation in a multilingual and multiracial community.

Although society is moving forwards, we cannot neglect the minority populations. The language barrier was not a valid reason to deprive our patient of treatment. Yet, unfortunately, individuals of minority races are less likely to access and receive quality mental health care.12 Additionally, many mainstream treatments, community support groups and resources cater to the general public and are not tailored to a specific race, language, or religious group. There is a need for these treatment resources to be customised. The mental health professional should be well versed in the relevant resources for both the ‘typical’ community and the ‘minority’ such as the patient.


This is the first case report of physical abuse of the recipient by the inducer in a country predominated by Chinese. There is an urgent need to explore possible forms of abuse among recipients of shared delusional disorder by the inducers.

It is surprising to learn that there remain a minority of individuals who appear to be confined to their home in a first world country where technology is so advanced and where education is compulsory. There is an immediate need to strengthen existing community support, to prevent psychiatric illnesses and enhance community psychiatric health. In our global society, mental health treatment should be available for all, regardless of race, nationality, language, or religion.


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