Shared psychotic disorder

Shared psychotic disorder was historically referred to as folie à deux. First coined by Lasegue and Falret in 1877, folie à deux describes the phenomena ‘of a transference of delusional ideas and/or abnormal behaviours from one person to one or more others who have been in close association with the primary patients’.¹ Presently it is represented in both the DSM-5 (as shared psychotic disorder) and in the ICD-11 (as induced delusional disorder). Despite this, it is still something of a rarity to see clinically, but this may not accurately reflect the prevalence among the general public as individuals often evade coming into contact with services as relatively sufficient levels of functioning are often maintained.²

Arnone et al. reviewed the demographics of those diagnosed with folie à deux.⁷ In their review of 42 cases between the years 1993 to 2005, they found that there did not appear to be any significant difference in gender between the secondaries, but a there was a higher incidence of women in the primary group. There were limited data on the family history and past psychiatric history of either patients in the reviews looked at. The nature of the relationship between both the primary and the secondary was well documented in the studies reviewed; 97.6% of the cases looked at were within the nuclear family, with only 2.4% occurring in friendships that had no genetic association. The most common relationship between the primary and the secondary was marriage (seen in 52.4% of cases) with a similar distribution between different genders. A parent and child relationship was seen in 31.1% of cases, and in 29.5% of cases the subjects were siblings.

The case below outlines patients presenting with a shared psychotic disorder; folie à deux; subtype A (see Table 1). The individuals had many of the risk factors that made them vulnerable to developing this condition. Their case is clinically interesting in the way the symptoms presented and evolved. The case is later discussed in the context of the current literature and the COVID-19 pandemic.

History

The two patients were a married couple. The wife was born the youngest of four daughters, two of whom are twins. Her parents separated when she was four years old following physical violence toward her mother from her father. Her mother then remarried. The patient described herself as shy at school. She enjoyed music and dance and had a good circle of friends. After school, she started working in sales in a department store before pursuing a career in modelling, acting and later sang in a band.

The husband was born as the youngest of three siblings and has lived in his family home since then. He felt ‘unloved’ by his parents and was treated poorly by his siblings, struggling to build or maintain a relationship with either of them, even into adulthood. Both his parents died of cancer and he cared for both while living with them.

The wife was previously in a marriage where she had experienced emotional abuse. They had two children prior to the relationship ending about 20 years ago; she had since brought up the two children independently. She then met her current husband when they both worked at a legal firm and describes their marriage as loving and happy. They have no children together and have lived together in the husband's terraced childhood home.

After the husband left his job as a paralegal he became self-employed setting up an internet bookshop. He stopped working when he became unwell and his wife currently works part time in a retail position. In December 2017, the husband was diagnosed with a rare type of basal cell carcinoma on his face, which is recurring and there is risk it could metastasise.

Presentation – the husband

The husband, a 57-year-old man, attended the emergency department with his wife due to concerns that he had not been eating or drinking and was expressing suicidal thoughts. During assessment by the mental health liaison team he disclosed he had not had anything to eat or drink for four days claiming he had ‘given up’ and ‘cannot take it anymore’. He was referring to current difficulties in his life and explained he had been ‘stalked and harassed’ by his neighbours for around 18 months, which had culminated in him wanting his life to be over.

The husband described the story and progression of the harassment in detail. Around 18 months prior to first assessment, around March 2020, the neighbours on the left of the husband and his wife reportedly began shouting through the walls. The husband described the neighbours as specifically targeting him, hearing them shout through the walls in the third person. This had worsened over time and they have started a running commentary of his movements.

The voices had been saying derogatory and defamatory things about him constantly. Closer to the time of first presentation, the husband said he woke one night and heard the neighbours saying they had hacked his computer, put pornography on it, and had access to both his bank and PayPal account. He immediately cancelled his credit cards and closed his bank account. He explained that the neighbours had put thermal cameras up so that they could see into his bathroom and broadcast the feed to a local channel.

It transpired that the couple had been living in darkness having covered up all their windows to prevent people from seeing in. They moved all their furniture into their living room and began living, eating and sleeping on an air mattress there. The husband had also called the police on a number of occasions to report this perceived harassment, and despite investigation, including speaking with the neighbours, they did not find any concerns or evidence. He had also recorded the sounds and voices of the neighbours as evidence and uploaded them to a social media platform.

The husband decided he no longer wanted to live when he sought support from his local church. He found that he could hear the neighbours in the church but was perplexed when they did not echo in the vast space. He also admitted to hearing them while at the hospital despite knowing this could not be possible. He has had no previous contact with mental health services and no history of alcohol or substance misuse. A CT head scan, physical examination and blood results were all within normal range with no unusual findings.

A collateral history from his wife revealed a highly distressed and highly anxious lady who corroborated her husband's take on events. She explained the neighbours on the other side of the house had been harassing her for around 10 years and she was also experiencing similar auditory hallucinations.

The husband stayed in the emergency department; despite taking olanzapine and mirtazapine, he continued to refuse to eat or drink. He maintained he could hear his neighbours speaking about him on the ward saying he was ‘mad’ and ‘should just die’.

The husband agreed to an informal admission, during which he made good progress on the above medication regimen, his auditory hallucinations eventually disappearing. However, during home leave, he became extremely stressed as the delusional beliefs and auditory hallucinations re-emerged.

He has not heard any voices since discharge from hospital and has been compliant with medication. He still believes that the neighbours targeted him in the past but explains them stopping owing to them having moved. He is engaging well with cognitive behavioural therapy (CBT) and applying for jobs in the local area.

Presentation – the wife

Concerns were raised for the 62-year-old wife at her husband's initial presentation. She was firstly encouraged to see her GP, who after assessment started her on propranolol. She was not referred to secondary services at this time. It later transpired she had withheld her main complaints and therefore the GP did not appreciate the full extent of her difficulties. She was first assessed by secondary mental health services in December 2021 following concerns raised by the ward staff when she visited her husband on the acute mental health ward. At this time, she described receiving constant harassment from her neighbours talking about her through the walls, taking control of her telephone conversations and laughing at her. She then began restricting her movements to only downstairs and endeavouring to be as quiet as possible to avoid the abuse she was hearing from her neighbours.

The wife reported the perceived abuse initially started from the right-side neighbours, an elderly woman and her son, who she has nicknamed ‘Hitler’. Around 10 years ago, the elderly woman's husband died and her adult son then moved in. Shortly after this, the patient began to hear this man talking about her and her husband through the walls, commenting on her movements and following her from room to room. At a similar time her relationship with her own son deteriorated adding to her social isolation.

Over time the patient reported that the frequency of the neighbours’ comments increased and the content of what they were saying became increasingly angry, hostile and derogatory. The patient felt that her neighbours’ motive was jealousy of her and her husband's loving and happy marriage. She explained that the neighbours will listen to them having sexual intercourse and make comments about it. In March 2021, the patient stated that the left-side neighbours then also began talking about her and her husband through the walls. The left side was a shared house of four men. The patient stated that of these four men, two were ‘good’ and two were ‘bad’. The two ‘bad’ men talked through the walls about her and her husband in the third person, also commenting on their movements but primarily commenting on her husband and stating he was a ‘paedophile’, that he was ‘looking at children’, and that they could see him masturbating. The two ‘good’ men would say more pleasant things and quash the others’ remarks. The patient believed these men began commenting after hearing the right-side neighbours’ remarks. The patient admitted that sometimes her husband could hear them and she could not but said this was only because of the acoustics in the house.

Initially the patient denied any personal or family history of mental health issues. However, it later transpired that her elder sister had schizophrenia and her daughter had depression. She reported having had mental health issues aged 18 years secondary to a sexual assault and having experienced an eating disorder while working as a model in her youth.

She was initially managed in the community on olanzapine. However, this was discontinued due to side-effects and changed to amisulpride. In March 2022, around four months after her husband was admitted informally, she also agreed to an informal admission. This was following her disclosing to professionals thoughts of harm toward her neighbours and revealing a suicide pact with her husband. After a month she was transferred to a rehabilitation ward. She remained pleasant and engaged with both ward staff and with activities throughout her admission, and utilised leave to visit her husband. During admission, her amisulpride was titrated up to 200mg twice daily. Her insight remained limited and persecutory beliefs around the neighbours remained, however, she was less distressed and preoccupied by this and her experiences of voice hearing reduced. She was discharged to the community in May 2022.

Following discharge from hospital, the patient has had good adherence to her medication regimen and has maintained little to no voice hearing experiences and her thoughts around her neighbours have reduced. She experienced a period of low mood, which improved with escitalopram and behavioural activation. She returned to her home and working part time in retail, and reported her relationship with her husband was increasingly positive. She remains convinced that the neighbours (mother and son) want to separate her and her husband. However, she has not heard them talking about her daily activities recently and is no longer preoccupied with them.

Discussion

In this interesting case of shared psychotic disorder, it seems the duration of untreated psychosis for the wife was over 10 years, whereas the husband appears to have developed the delusional beliefs over the course of 18 months. The case, beginning with the husband's presentation as one of depression and suicidal ideation, developed into a more complex picture of shared delusions and supporting each other's persecutory belief system.

There are certain characteristics that are often associated with each individual in the shared psychotic disorder relationship; ^{7, 8} the primary (in this case the wife) is traditionally the more dominant individual, and the secondary (the husband) more dependent.⁹ We noted that the husband was a quiet, passive man compared with his wife who appeared to be the more dominant of the two.

The diagnosis of the primary is often schizophrenia or delusional disorder. As in this case persecutory delusions tend to be the predominant feature of shared psychotic disorder in both the primary and the secondary.¹⁰ According to the literature hallucinations are most commonly observed in primaries, and less commonly reported in the secondary. As discussed, auditory hallucinations were a feature of the husband's and the wife's psychopathology. Recent studies note that hallucinations have been identified in up to 50% of secondaries.^{7, 11, 12} When they do occur they are most commonly auditory hallucinations ^{7, 11, 12} or visual hallucinations in the context of delusional parasitosis.¹³ Interestingly there have been two case reports of the secondary experiencing hallucinations while the primary did not.¹⁴

The husband had several risk factors rendering him more vulnerable to developing a shared psychosis. Balducci et al.¹⁰ noted several features that make an individual susceptible to developing the exogenous symptoms: a dependent personality; a learning or physical disability; stressful early life events,¹⁵ and dementia. Additionally, there have been studies that have suggested that a possible genetic disposition towards schizophrenia can play a role in someone going on to develop shared psychotic disorder. This is especially seen in twins and first-degree relatives suffering from the condition.⁴ The husband reported a traumatic upbringing where he was bullied by his siblings, and described cold parents who punished him for expressing emotion. Childhood trauma has a well established link with psychosis,¹⁶ increasing the husband's risk of developing psychotic phenomena independently and a vulnerability to developing a shared psychosis.

Social isolation has been identified as a major risk factor for the development of shared psychosis^{4, 7, 8, 12} with Silvera finding this to be present in 67.3% of cases.¹² The influence of the primary on the secondary appears to have more impact when both parties are removed from societal norms. In the case of our couple, they experienced social isolation in the context of the COVID-19 pandemic. Additionally, the husband had a diagnosis of a rare form of skin cancer resulting in him becoming housebound. He later closed his home business and became unemployed. Furthermore social isolation has been shown to increase paranoia in individuals with psychosis.⁸ In this case it enhanced the unusual closeness of relationship between husband and wife.⁷

There are currently limited data relating to shared psychosis in the context of the pandemic; Kawaskai et al.¹⁷ described a case of a mother and daughter who developed shared delusions during their isolation secondary to self-quarantine in the COVID-19 pandemic. In this case, the mother met the criteria for a diagnosis of schizophrenia but it was concluded that the daughter's (the secondary) experiences were psychosis by association with the primary. It will be interesting to see if more cases are reported as we begin to disentangle the impact of COVID-19 lockdown on mental health and society as a whole.

Traditionally separation from the primary was thought to be the mainstay of treatment and would halt the secondary's delusions. However, through reviews of case reports it has been shown that separation alone is insufficient.¹⁴ Inpatient treatment comprising separation and pharmacotherapy with antipsychotics was needed for both primaries and secondaries in a recent review of case reports.¹¹ As in the case discussed, the patients tend to be related or spouses and so separation is rarely an appropriate long-term plan. Menculini et al.¹¹ found conflicting evidence relating to remission and separation. One paper looking at children and adolescents found that separation was not related to clinical remission, while a separate paper found that, in some cases, separation appeared to be sufficient for gaining remission in some secondary patients.¹¹ The aim of treatment is to treat the primary sufficiently to ensure that when separation is ceased, they are not influencing the secondary to the point of psychosis.

On his return home the husband in our case faced additional difficulties as he struggled to process the traumatic memories of his previous experiences. Currently both wife and husband are supported in the home environment. It is hoped with the appropriate use of medications, reducing their social isolation via activity scheduling and support from the community team they will continue to make a sustained recovery.

Meeting the wife in our case made it clear that she was the primary and had been unwell for a number of years, but due to the couple's relative social isolation it had gone unnoticed and untreated. The catalyst of COVID-19, the husband's cancer diagnosis and loss of work led to him becoming psychotic and taking on his wife's delusions.

This case gives an insight into an otherwise rarely seen presentation and documenting how it developed over a number of years it illustrates how life stressors and social isolation contributed to the development of this curious case of shared psychotic disorder.

Patient consent

Patient consent was gained to publish details about their case.

Declaration of interests

No conflicts of interest were declared.