What is Delusional Parasitosis?


Delusional parasitosis (DP) is a mental disorder in which individuals have a persistent belief that they are infested with living or non-living pathogens such as parasites, insects, or bugs, when no such infestation is present.

They usually report tactile hallucinations known as formication, a sensation resembling insects crawling on or under the skin. Morgellons is considered to be a subtype of this condition, in which individuals have sores that they believe contain harmful fibres.

Delusional parasitosis is classified as a delusional disorder in the Diagnostic and Statistical Manual of Mental Disorders (DSM5). The cause is unknown, but is thought to be related to excess dopamine in the brain. Delusional parasitosis is diagnosed when the delusion is the only symptom of psychosis and the delusion – that cannot be better explained by another condition – has lasted a month or longer. Few individuals with the condition willingly accept treatment, because they do not recognise the illness as a delusion. Antipsychotic medications offer a cure, while cognitive behavioural therapy and antidepressants can be used to help alleviate symptoms.

The condition is rare, and is observed twice as often in women as men. The average age of people with the disorder is 57. An alternative name, Ekbom’s syndrome, refers to the neurologist Karl-Axel Ekbom, who published seminal accounts of the disease in 1937 and 1938.


Delusional infestation is classified as a delusional disorder of the somatic subtype in the Diagnostic and Statistical Manual of Mental Disorders (DSM5). The name delusional parasitosis has been the most common name since 2015, but the condition has also been called delusional infestation, delusory parasitosis, delusional ectoparasitosis, psychogenic parasitosis, Ekbom syndrome, dermatophobia, parasitophobia, formication and “cocaine bugs”.

Morgellons is a form of delusional parasitosis in which people have painful skin sensations that they believe contain fibres of various kinds; its presentation is very similar to other delusional infestations, but people with this self-diagnosed condition also believe that strings or fibres are present in their skin lesions.

Delusory cleptoparasitosis is a form of delusion of parasitosis where the person believes the infestation is in their dwelling, rather than on or in their body.


While a rare disorder, delusional parasitosis is the most common of the hypochondriacal psychoses, after other types of delusions such as body odour or halitosis. It may be undetected because those who have it do not see a psychiatrist because they do not recognise the condition as a delusion. A population-based study in Olmsted County, Minnesota found a prevalence of 27 per 100,000 person-years and an incidence of almost 2 cases per 100,000 person-years. The majority of dermatologists will see at least one person with DP during their career.

It is observed twice as often in women than men. The highest incidence occurs in people in their 60s, but there is also a higher occurrence in people in their 30s, associated with substance use. It occurs most often in “socially isolated” women with an average age of 57.

Since the early 2000s, a strong internet presence has led to increasing self-diagnosis of Morgellons.

Brief History

Karl-Axel Ekbom, a Swedish neurologist, first described delusional parasitosis as “pre-senile delusion of infestation” in 1937. The common name has changed many times since then. Ekbom originally used the German word dermatozoenwahn, but other countries used the term Ekbom’s syndrome. That term fell out of favour because it also referred to restless legs syndrome. Other names that referenced “phobia” were rejected because anxiety disorder was not typical of the symptoms. The eponymous Ekbom’s disease was changed to “delusions of parasitosis” in 1946 in the English literature, when researchers J Wilson and H Miller described a series of cases, and to “delusional infestation” in 2009. The most common name since 2015 has been “delusional parasitosis”.

Ekbom’s original was translated to English in 2003; the authors hypothesized that James Harrington (1611-1677) may have been the “first recorded person to suffer from such delusions when he ‘began to imagine that his sweat turned to flies, and sometimes to bees and other insects’.”


Mary Leitao, the founder of the Morgellons Research Foundation, coined the name Morgellons in 2002, reviving it from a letter written by a physician in the mid-1600s. Leitao and others involved in her foundation (who self-identified as having Morgellons) successfully lobbied members of the US Congress and the US Centres for Disease Control and Prevention (CDC) to investigate the condition in 2006. The CDC published the results of its multi-year study in January 2012. The study found no underlying infectious condition and few disease organisms were present in people with Morgellons; the fibres found were likely cotton, and the condition was “similar to more commonly recognized conditions such as delusional infestation”.

An active online community has supported the notion that Morgellons is an infectious disease, and propose an association with Lyme disease. Publications “largely from a single group of investigators” describe findings of spirochetes, keratin and collagen in skin samples of a small number of individuals; these findings are contradicted by the much larger studies conducted by the CDC.

Signs and Symptoms

People with delusional parasitosis believe that “parasites, worms, mites, bacteria, fungus” or some other living organism has infected them, and reasoning or logic will not dissuade them from this belief. Details vary among those who have the condition, though it typically manifests as a crawling and pin-pricking sensation that is most commonly described as involving perceived parasites crawling upon or burrowing into the skin, sometimes accompanied by an actual physical sensation (known as formication). Affected people may injure themselves in attempts to be rid of the “parasites”; resulting skin damage includes excoriation, bruising and cuts, as well as damage caused from using chemical substances and obsessive cleansing routines.

A “preceding event such as a bug bite, travel, sharing clothes, or contact with an infected person” is often identified by individuals with DP; such events may lead the individual to misattribute symptoms because of more awareness of symptoms they were previously able to ignore. Nearly any marking upon the skin, or small object or particle found on the person or their clothing, can be interpreted as evidence for the parasitic infestation, and individuals with the condition commonly compulsively gather such “evidence” to present to medical professionals. This presentation is known as the “matchbox sign”, “Ziploc bag sign” or “specimen sign”, because the “evidence” is frequently presented in a small container, such as a matchbox. The matchbox sign is present in five to eight out of every ten people with DP. Related is a “digital specimen sign”, in which individuals bring collections of photographs to document their condition.

Similar delusions may be present in close relatives – a shared condition known as a folie à deux – that occurs in 5 to 15% of cases and is considered a shared psychotic disorder. Because the internet and the media contribute to furthering shared delusions, DP has also been called folie à Internet; when affected people are separated, their symptoms typically subside, but most still require treatment.

Approximately eight out of ten individuals with DP have co-occurring conditions – mainly depression, followed by substance abuse and anxiety; their personal and professional lives are frequently disrupted as they are extremely distressed about their symptoms.

A 2011 Mayo Clinic study of 108 patients failed to find evidence of skin infestation in skin biopsies and patient-provided specimens; the study concluded that the feeling of skin infestation was DP.


The cause of delusional parasitosis is unknown. It may be related to excess dopamine in the brain’s striatum, resulting from diminished dopamine transporter (DAT) function, which regulates dopamine reuptake in the brain. Evidence supporting the dopamine theory is that medications that inhibit dopamine reuptake (for example cocaine and amphetamines) are known to induce symptoms such as formication. Other conditions that also demonstrate reduced DAT functioning are known to cause secondary DP; these conditions include “schizophrenia, depression, traumatic brain injury, alcoholism, Parkinson’s and Huntington’s diseases, human immunodeficiency virus infection, and iron deficiency”. Further evidence is that antipsychotics improve DP symptoms, which may be because they affect dopamine transmission.


Delusional parasitosis is diagnosed when the delusion is the only symptom of psychosis, the delusion has lasted a month or longer, behaviour is otherwise not markedly odd or impaired, mood disorders – if present at any time – have been comparatively brief, and the delusion cannot be better explained by another medical condition, mental disorder, or the effects of a substance. For diagnosis, the individual must attribute abnormal skin sensations to the belief that they have an infestation, and be convinced that they have an infestation even when evidence shows they do not.

The condition is recognised in two forms:

  • Primary delusional parasitosis: The delusions are the only manifestation of a psychiatric disorder.
  • Secondary delusional parasitosis: This occurs when another psychiatric condition, medical illness or substance (medical or recreational) use causes the symptoms; in these cases, the delusion is a symptom of another condition rather than the disorder itself.
    • Secondary forms of DP can be functional (due to mainly psychiatric disorders) or organic (due to other medical illness or organic disease.
    • The secondary organic form may be related to vitamin B12 deficiency, hypothyroidism, anaemia, hepatitis, diabetes, HIV/AIDS, syphilis, or abuse of cocaine.

Examination to rule out other causes is key to diagnosis. Parasitic infestations are ruled out via skin examination and laboratory analyses. Bacterial infections may be present as a result of the individual constantly manipulating their skin. Other conditions that can cause itching skin are also ruled out; this includes a review of medications that may lead to similar symptoms. Testing to rule out other conditions helps build a trusting relationship with the physician; this can include laboratory analysis such as a complete blood count, comprehensive metabolic panel, erythrocyte sedimentation rate, C-reactive protein, urinalysis for toxicology and thyroid-stimulating hormone, in addition to skin biopsies and dermatological tests to detect or rule out parasitic infestations. Depending on symptoms, tests may be done for “human immunodeficiency virus, syphilis, viral hepatitis, B12 or folate deficiency,” and allergies.

Differential Diagnosis

Delusional parasitosis must be distinguished from scabies, mites, and other psychiatric conditions that may occur along with the delusion; these include schizophrenia, dementia, anxiety disorders, obsessive-compulsive disorder, and affective or substance-induced psychoses or other conditions such as anaemia that may cause psychosis.

Pruritus and other skin conditions are most commonly caused by mites, but may also be caused by “grocer’s itch” from agricultural products, pet-induced dermatitis, caterpillar/moth dermatitis, or exposure to fiberglass. Several drugs, legal or illegal, such as amphetamines, dopamine agonists, opioids, and cocaine may also cause the skin sensations reported. Diseases that must be ruled out in differential diagnosis include hypothyroidism, and kidney or liver disease. Many of these physiological factors, as well as environmental factors such as airborne irritants, are capable of inducing a “crawling” sensation in otherwise healthy individuals; some people become fixated on the sensation and its possible meaning, and this fixation may then develop into DP.


As of 2019, there have not been any studies that compare available treatments to placebo. The only treatment that provides a cure, and the most effective treatment, is low doses of antipsychotic medication. Cognitive behavioural therapy (CBT) can also be useful. Risperidone is the treatment of choice. For many years, the treatment of choice was pimozide, but it has a higher side effect profile than the newer antipsychotics. Aripiprazole and ziprasidone are effective but have not been well studied for delusional parasitosis. Olanzapine is also effective. All are used at the lowest possible dosage, and increased gradually until symptoms remit.

People with the condition often reject the professional medical diagnosis of delusional parasitosis, and few willingly undergo treatment, despite demonstrable efficacy, making the condition difficult to manage. Reassuring the individual with DP that there is no evidence of infestation is usually ineffective, as the patient may reject that. Because individuals with DP typically see many physicians with different specialties, and feel a sense of isolation and depression, gaining the patient’s trust, and collaborating with other physicians, are key parts of the treatment approach. Dermatologists may have more success introducing the use of medication as a way to alleviate the distress of itching. Directly confronting individuals about delusions is unhelpful because by definition, the delusions are not likely to change; confrontation of beliefs via CBT is accomplished in those who are open to psychotherapy. A five-phase approach to treatment is outlined by Heller et al. (2013) that seeks to establish rapport and trust between physician and patient.


The average duration of the condition is about three years. The condition leads to social isolation and affects employment. Cure may be achieved with antipsychotics or by treating underlying psychiatric conditions.

Society and Culture

Jay Traver (1894-1974), a University of Massachusetts entomologist, was known for “one of the most remarkable mistakes ever published in a scientific entomological journal”, after publishing a 1951 account of what she called a mite infestation which was later shown to be incorrect, and that has been described by others as a classic case of delusional parasitosis as evidenced by her own detailed description. Matan Shelomi argues that the historical paper should be retracted because it has misled people about their delusion. He says the paper has done “permanent and lasting damage” to people with delusional parasitosis, “who widely circulate and cite articles such as Traver’s and other pseudoscientific or false reports” via the internet, making treatment and cure more difficult.

Shelomi published another study in 2013 of what he called scientific misconduct when a 2004 article in the Journal of the New York Entomological Society included what he says is photo manipulation of a matchbox specimen to support the claim that individuals with DP are infested with collembola.

This page is based on the copyrighted Wikipedia article < https://en.wikipedia.org/wiki/Delusional_parasitosis >; it is used under the Creative Commons Attribution-ShareAlike 3.0 Unported License (CC-BY-SA). You may redistribute it, verbatim or modified, providing that you comply with the terms of the CC-BY-SA.

What is Paraphrenia?


Paraphrenia is a mental disorder characterised by an organised system of paranoid delusions with or without hallucinations (the positive symptoms of schizophrenia) and without deterioration of intellect or personality (its negative symptom).

This disorder is also distinguished from schizophrenia by a lower hereditary occurrence, less premorbid maladjustment, and a slower rate of progression. Onset of symptoms generally occurs later in life, near the age of 60. The prevalence of the disorder among the elderly is between 0.1% and 4%.

Paraphrenia is not included in the DSM-5; psychiatrists often diagnose patients presenting with paraphrenia as having atypical psychosis, delusional disorder, psychosis not otherwise specified, schizoaffective disorders, and persistent persecutory states of older adults. Recently, mental health professionals have also been classifying paraphrenia as very late-onset schizophrenia-like psychosis.

In the Russian psychiatric manuals, paraphrenia (or paraphrenic syndrome) is the last stage of development of paranoid schizophrenia. “Systematised paraphrenia” (with systematised delusions i. e. delusions with complex logical structure) and “expansive-paranoid paraphrenia” (with expansive/grandiose delusions and persecutory delusions) are the variants of paranoid schizophrenia (F20.0). Sometimes systematised paraphrenia can be seen with delusional disorder (F22.0). The word is from Ancient Greek: παρά – beside, near + φρήν – intellect, mind.

Brief History

The term paraphrenia was originally popularised by Karl Ludwig Kahlbaum in 1863 to describe the tendency of certain psychiatric disorders to occur during certain transitional periods in life (describing paraphrenia hebetica as the insanity of the adolescence and paraphrenia senilis as the insanity of the elders.

The term was also used by Sigmund Freud for a short time starting in 1911 as an alternative to the terms schizophrenia and dementia praecox, which in his estimation did not correctly identify the underlying condition, and by Emil Kraepelin in 1912/1913, who changed its meaning to describe paraphrenia as it is understood today, as a small group of individuals that have many of the symptoms of schizophrenia with a lack of deterioration and thought disorder. Kraepelin’s study was discredited by Wilhelm Mayer in 1921 when he conducted a follow-up study using Kraepelin’s data. His study suggested that there was little to no discrimination between schizophrenia and paraphrenia; given enough time, patients presenting with paraphrenia will merge into the schizophrenic pool. However, Meyer’s data are open to various interpretations. In 1952, Roth and Morrissey conducted a large study in which they surveyed the mental hospital admissions of older patients. They characterised patients as having:

“paraphrenic delusions which… occurred in each case in the setting of a well-preserved intellect and personality, were often ‘primary’ in character, and were usually associated with the passivity failings or other volitional disturbances and hallucinations in clear consciousness pathognomonic of schizophrenia”.

In recent medicine, the term paraphrenia has been replaced by the diagnosis of “very late-onset schizophrenia-like psychosis” and has also been called “atypical psychoses, delusional disorder, psychoses not otherwise specified, schizoaffective disorders, and persistent persecutory states of older adults” by psychotherapists.[4] Current studies, however, recognize the condition as “a viable diagnostic entity that is distinct from schizophrenia, with organic factors playing a role in a significant portion of patients.”[4]

Signs and Symptoms

The main symptoms of paraphrenia are paranoid delusions and hallucinations. The delusions often involve the individual being the subject of persecution, although they can also be erotic, hypochondriacal, or grandiose in nature. The majority of hallucinations associated with paraphrenia are auditory, with 75% of patients reporting such an experience; however, visual, tactile, and olfactory hallucinations have also been reported. The paranoia and hallucinations can combine in the form of “threatening or accusatory voices coming from neighbouring houses [and] are frequently reported by the patients as disturbing and undeserved”. Patients also present with a lack of symptoms commonly found in other mental disorders similar to paraphrenia. There is no significant deterioration of intellect, personality, or habits and patients often remain clean and mostly self-sufficient. Patients also remain oriented well in time and space.

Paraphrenia is different from schizophrenia because, while both disorders result in delusions and hallucinations, individuals with schizophrenia exhibit changes and deterioration of personality whereas individuals with paraphrenia maintain a well-preserved personality and affective response.



Paraphrenia is often associated with a physical change in the brain, such as a tumour, stroke, ventricular enlargement, or neurodegenerative process. Research that reviewed the relationship between organic brain lesions and the development of delusions suggested that “brain lesions which lead to subcortical dysfunction could produce delusions when elaborated by an intact cortex”.

Predisposing Factors

Many patients who present with paraphrenia have significant auditory or visual loss, are socially isolated with a lack of social contact, do not have a permanent home, are unmarried and without children, and have maladaptive personality traits. While these factors do not cause paraphrenia, they do make individuals more likely to develop the disorder later in life.


While the diagnosis of paraphrenia is absent from recent revisions of the DSM and the ICD, many studies have recognised the condition as “a viable diagnostic entity that is distinct from schizophrenia, with organic factors playing a role in a significant portion of patients.” As such, paraphrenia is seen as being distinct from both schizophrenia and progressive dementia in old age. Ravindran (1999) developed a list of criteria for the diagnosis of paraphrenia, which agrees with much of the research done up to the time it was published.

  1. A delusional disorder of at least six months duration characterized by the following:
    1. Preoccupation with one or more semi-systematised delusions, often accompanied by auditory hallucinations.
    2. Affect notably well-preserved and appropriate. Ability to maintain rapport with others.
    3. None of:
      1. Intellectual deterioration.
      2. Visual hallucinations.
      3. Incoherence.
      4. Flat or grossly inappropriate affect.
      5. Grossly disorganised behaviour at times other than during the acute episode.
    4. Disturbance of behaviour understandable in relation to the content of the delusions and hallucinations.
    5. Only partly meets criterion A for schizophrenia. No significant organic brain disorder.


Research suggests that paraphrenics respond well to antipsychotic drug therapy if doctors can successfully achieve sufficient compliance. Herbert found that Stelazine combined with Disipal was an effective treatment. It promoted the discharging of patients and kept discharged patients from being readmitted later. While behaviour therapy may help patients reduce their preoccupation with delusions, psychotherapy is not currently of primary value.


Individuals who develop paraphrenia have a life expectancy similar to the normal population. Recovery from the psychotic symptoms seems to be rare, and in most cases paraphrenia results in in-patient status for the remainder of the life of the patient. Patients experience a slow deterioration of cognitive functions and the disorder can lead to dementia in some cases, but this development is no greater than the normal population.


Studies suggest that the prevalence of paraphrenia in the elderly population is around 2-4%.

Sex Differences

While paraphrenia can occur in both men and women, it is more common in women, even after the difference has been adjusted for life expectancies. The ratio of women with paraphrenia to men with paraphrenia is anywhere from 3:1 to 45:2.


It is seen mainly in patients over the age of 60, but has been known to occur in patients in their 40s and 50s.

Personality Type and Living Situation

It is suggested that individuals who develop paraphrenia later in life have premorbid personalities, and can be described as “quarrelsome, religious, suspicious or sensitive, unsociable and cold-hearted.” Many patients were also described as being solitary, eccentric, isolated and difficult individuals; these characteristics were also long-standing rather than introduced by the disorder. Most of the traits recognised prior to the onset of paraphrenia in individuals can be grouped as either paranoid or schizoid. Patients presenting with paraphrenia were most often found to be living by themselves (either single, widowed, or divorced). There have also been reports of low marriage rate among paraphrenics and these individuals also have few or no children (possibly because of this premorbid personality).

Physical Factors

The development of paranoia and hallucinations in old age have been related to both auditory and visual impairment, and individuals with paraphrenia often present with one or both of these impairments. Hearing loss in paraphrenics is associated with early age of onset, long duration, and profound auditory loss.

This page is based on the copyrighted Wikipedia article < https://en.wikipedia.org/wiki/Paraphrenia >; it is used under the Creative Commons Attribution-ShareAlike 3.0 Unported License (CC-BY-SA). You may redistribute it, verbatim or modified, providing that you comply with the terms of the CC-BY-SA.

What is Folie à Deux?


Folie à deux (‘folly of two’, or ‘madness [shared] by two’), also known as shared psychosis or shared delusional disorder (SDD), is a psychiatric syndrome in which symptoms of a delusional belief, and sometimes hallucinations, are transmitted from one individual to another.

The same syndrome shared by more than two people may be called folie à… trois (‘three’) or quatre (‘four’); and further, folie en famille (‘family madness’) or even folie à plusieurs (‘madness of several’).

The disorder was first conceptualised in 19th-century French psychiatry by Charles Lasègue and Jules Falret and is also known as Lasègue-Falret syndrome.

Recent psychiatric classifications refer to the syndrome as shared psychotic disorder (DSM-4 – 297.3) and induced delusional disorder (ICD-10 – F24), although the research literature largely uses the original name.

This disorder is not in the current DSM (DSM-5), which considers the criteria to be insufficient or inadequate. DSM-5 does not consider Shared Psychotic Disorder (Folie à Deux) as a separate entity, but rather, the physician should classify it as “Delusional Disorder” or in the “Other Specified Schizophrenia Spectrum and Other Psychotic Disorder”.

Signs and Symptoms

This syndrome is most commonly diagnosed when the two or more individuals of concern live in proximity, may be socially or physically isolated, and have little interaction with other people.

Various sub-classifications of folie à deux have been proposed to describe how the delusional belief comes to be held by more than one person:

  • Folie imposée:
    • Where a dominant person (known as the ‘primary’, ‘inducer’ or ‘principal’) initially forms a delusional belief during a psychotic episode and imposes it on another person or persons (the ‘secondary’, ‘acceptor’, or ‘associate’), with the assumption that the secondary person might not have become deluded if left to his or her own devices.
    • If the parties are admitted to hospital separately, then the delusions in the person with the induced beliefs usually resolve without the need of medication.
  • Folie simultanée:
    • Either the situation where two people considered to suffer independently from psychosis influence the content of each other’s delusions so they become identical or strikingly similar, or one in which two people “morbidly predisposed” to delusional psychosis mutually trigger symptoms in each other.

Folie à deux and its more populous derivatives are in many ways a psychiatric curiosity. The current Diagnostic and Statistical Manual of Mental Disorders states that a person cannot be diagnosed as being delusional if the belief in question is one “ordinarily accepted by other members of the person’s culture or subculture.” It is not clear at what point a belief considered to be delusional escapes from the folie à… diagnostic category and becomes legitimate because of the number of people holding it. When a large number of people may come to believe obviously false and potentially distressing things based purely on hearsay, these beliefs are not considered to be clinical delusions by the psychiatric profession, and are instead labelled as mass hysteria.

As with most psychological disorders, the extent and type of delusion varies, but the non-dominant person’s delusional symptoms usually resemble those of the inducer. Prior to therapeutic interventions, the inducer typically does not realise that they are causing harm, but instead believe they are helping the second person to become aware of vital or otherwise notable information.

Types of Delusion

Psychology Today magazine defines delusions as “fixed beliefs that do not change, even when a person is presented with conflicting evidence.” Types of delusion include:

Bizarre DelusionsThose which are clearly implausible and not understood by peers within the same culture, even those with psychological disorders; for example, if one thought that all of their organs had been taken out and replaced by someone else’s while they were asleep without leaving any scar and without their waking up. It would be impossible to survive such a procedure, and even surgery involving transplantation of multiple organs would leave the person with severe pain, visible scars, etc.
Non-Bizarre DelusionsCommon among those with personality disorders and are understood by people within the same culture. For example, unsubstantiated or unverifiable claims of being followed by the FBI in unmarked cars and watched via security cameras would be classified as a non-bizarre delusion; while it would be unlikely for the average person to experience such a predicament, it is possible, and therefore understood by those around them.
Mood-Congruent DelusionsThese correspond to a person’s emotions within a given timeframe, especially during an episode of mania or depression. For example, someone with this type of delusion may believe with certainty that they will win $1 million at the casino on a specific night, despite lacking any way to see the future or influence the probability of such an event. Similarly, someone in a depressive state may feel certain that their mother will get hit by lightning the next day, again in spite of having no means of predicting or controlling future events.
Mood-Neutral DelusionsThese are unaffected by mood, and can be bizarre or non-bizarre; the formal definition provided by Mental Health Daily is “a false belief that isn’t directly related to the person’s emotional state.” An example would be a person who is convinced that somebody has switched bodies with their neighbour, the belief persisting irrespective of changes in emotional status.

Biopsychosocial Effects

As with many psychiatric disorders, shared delusional disorder can negatively impact the psychological and social aspects of a person’s wellbeing. Unresolved stress resulting from a delusional disorder will eventually contribute to or increase the risk of other negative health outcomes, such as cardiovascular disease, diabetes, obesity, immunological problems, and others. These health risks increase with the severity of the disease, especially if an affected person does not receive or comply with adequate treatment.

Persons with a delusional disorder have a significantly high risk of developing psychiatric comorbidities such as depression and anxiety. This may be attributable to a genetic pattern shared by 55% of SDD patients.

Shared delusional disorder can have a profoundly negative impact on a person’s quality of life. Persons diagnosed with a mental health disorder commonly experience social isolation, which is detrimental to psychological health. This is especially problematic with SDD, as social isolation contributes to the onset of the disorder; in particular, relapse is likely if returning to an isolated living situation, in which shared delusions can be reinstated.


While the exact causes of SDD are unknown, the main two contributors are stress and social isolation.

People who are socially isolated together tend to become dependent on those they are with, leading to an inducers influence on those around them. Additionally, people developing shared delusional disorder do not have others reminding them that their delusions are either impossible or unlikely. As a result, treatment for shared delusional disorder includes those affected be removed from the inducer.

Stress is also a factor, as it is a common factor in mental illness developing or worsening. The majority of people that develop shared delusional disorder are genetically predisposed to mental illness, but this predisposition is not enough to develop a mental disorder. However, stress can increase the risk of this disorder. When stressed, an individual’s adrenal gland releases the “stress hormone” cortisol into the body, increasing the brain’s level of dopamine; this change can be linked to the development of a mental illness, such as a shared delusional disorder.


SDD is often difficult to diagnose. Usually, the person with the condition does not seek out treatment, as they do not realise that their delusion is abnormal, as it comes from someone in a dominant position who they trust. Furthermore, since their delusion comes on gradually and grows in strength over time, their doubt is slowly weakened during this time. SDD is diagnosed using the DSM-5, and according to this, the patient must meet three criteria:

  • They must have a delusion that develops in the context of a close relationship with an individual with an already established delusion.
  • The delusion must be very similar or even identical to the one already established one that the primary case has.
  • The delusion cannot be better explained by any other psychological disorder, mood disorder with psychological features, a direct result of physiological effects of substance abuse or any general medical condition.

Related phenomena

Reports have stated that a phenomenon similar to folie à deux was induced by the military incapacitating agent BZ in the late 1960s.


SDD is most commonly found in women with slightly above-average IQs, who are isolated from their family, and who are in relationships with a dominant person who has delusions. The majority of secondary cases (people who develop the shared delusion) also meet the criteria for Dependent Personality Disorder, which is characterised by a pervasive fear that leads them to need constant reassurance, support, and guidance. Additionally, 55% of secondary cases had a relative with a psychological disorder that included delusions and, as a result, the secondary cases are usually susceptible to mental illness.


After a person has been diagnosed, the next step is to determine the proper course of treatment. The first step is to separate the formerly healthy person from the inducer, and see if the delusion goes away or lessens over time. If this is not enough to stop the delusions, there are two possible courses of action: Medication or therapy, which is then broken down into personal therapy and/or family therapy.

With treatment, the delusions, and therefore the disease, will eventually lessen so much so, that it will practically disappear in most cases. However, if left untreated, it can become chronic and lead to anxiety, depression, aggressive behaviour, and further social isolation. Unfortunately, there are not many statistics about the prognosis of shared delusional disorder, as it is a rare disease, and it is expected that the majority of cases go unreported; however, with treatment, the prognosis is very good.


If the separation alone is not working, antipsychotics are often prescribed for a short time to prevent the delusions. Antipsychotics are medications that reduce or relieve symptoms of psychosis such as delusions or hallucinations (seeing or hearing something that is not there). Other uses of antipsychotics include stabilising moods for people with mood swings and mood disorders (i.e. in bipolar patients), reducing anxiety in anxiety disorders, and lessening tics in people with Tourettes. Antipsychotics do not cure psychosis, but they do help reduce symptoms; when paired with therapy, the person with the condition has the best chance of recovering. While antipsychotics are powerful, and often effective, they do have side effects, such as inducing involuntary movements. They should only be taken if absolutely required, and under the supervision of a psychiatrist.


The two most common forms of therapy for people with shared delusional disorder are personal and family therapy.

  • Personal therapy:
    • Is one-on-one counselling that focuses on building a relationship between the counsellor and the patient, and aims to create a positive environment where the patient feels that they can speak freely and truthfully.
    • This is advantageous, as the counsellor can usually get more information out of the patient to get a better idea of how to help them.
    • Additionally, if the patient trusts what the counsellor says, disproving the delusion will be easier.
  • Family therapy:
    • Is a technique in which the entire family comes into therapy together to work on their relationships, and to find ways to eliminate the delusion within the family dynamic.
    • For example, if someone’s sister is the inducer, the family will have to get involved to ensure the two stay apart, and to sort out how the family dynamic will work around that.
    • The more support a patient has, the more likely they are to recover, especially since SDD usually occurs due to social isolation.

Notable Cases

  • In May 2008, in the case of twin sisters Ursula and Sabina Eriksson, Ursula ran into the path of an oncoming articulated lorry, sustaining severe injuries.
    • Sabina then immediately duplicated her twin’s actions by stepping into the path of an oncoming car; both sisters survived the incident with severe but non-life-threatening injuries.
    • It was later claimed that Sabina Eriksson was a ‘secondary’ sufferer of folie à deux, influenced by the presence or perceived presence of her twin sister, Ursula – the ‘primary’. Sabina later told an officer at the police station, “We say in Sweden that an accident rarely comes alone. Usually at least one more follows—maybe two.”
    • However, upon her release from hospital, Sabina behaved erratically before stabbing a man to death.
  • Another case involved a married couple by the name of Margaret and Michael, both aged 34 years, who were discovered to have folie à deux when they were both found to be sharing similar persecutory delusions.
    • They believed that certain persons were entering their house, spreading dust and fluff, and “wearing down their shoes.”
    • Both had, in addition, other symptoms supporting a diagnosis of emotional contagion, which could be made independently in either case.
  • Psychiatrist Reginald Medlicott published an article about the Parker-Hulme murder case, called “Paranoia of the Exalted Type in a Setting of Folie a Deux – A Study of Two Adolescent Homicides”, arguing that the intense relationship and shared fantasy world of the two teenaged friends reinforced and exacerbated the mental illness that led to the murder: “each acted on the other as a resonator, increasing the pitch of their narcissism.”
  • In 2016, a case involving a family of five from Melbourne, Australia made headlines when they abruptly fled their home and travelled more than 1,600 km (1,000 mi) across the state of Victoria, because some of the family had become convinced someone was out to kill and rob them.
    • No such evidence was found by the police, and the symptoms of those involved resolved on their own once the family returned to their home.
  • The book Bad Blood: Secrets and Lies in a Silicon Valley Startup suggests that this ailment plagued the founder of Theranos, Elizabeth Holmes, and her boyfriend and business partner, Ramesh Balwani.
  • It was suspected a family of eleven members from Burari, India had this condition.
    • On 30 June 2018, the family died by mass suicide due to the shared belief of one of its members.
  • Psychologists H. O’Connell and P.G. Doyle believe folie à plusieurs to have been at least a partial factor in the murder of Bridget Cleary.
    • In 1895, Michael Cleary convinced several friends and relatives that his wife, Bridget Cleary, was a changeling who had been replaced by a fairy.
    • They assisted him in physically abusing her to “cast the fairies” out, before he ultimately burned her to death shortly afterwards.
  • Christine and Léa Papin were two French sisters who, as live-in maids, were convicted of murdering their employer’s wife and daughter in Le Mans, France on 02 February 1933.

In Popular Culture

  • “Folie à Deux” is the title of the nineteenth episode in the fifth season of The X-Files (1998). The episode details a story of a man who believes his boss is an insect monster, a delusion that Fox Mulder begins to share after investigation.
  • Bug (2006) is a film that depicts a couple with a shared delusion that aphids are living under their skin.
  • In Season 2, Episode 3 of Criminal Minds, “The Perfect Storm” (2006), Dr. Reid mentions that the rapists had this condition.
  • In 2008, American rock band Fall Out Boy released their fourth album, Folie à Deux.
  • The independent film Apart (2011) depicts two lovers affected and diagnosed with induced delusional disorder, trying to uncover a mysterious and tragic past they share. In a 2011 interview, director Aaron Rottinghaus stated the film was based on research from actual case studies.
  • In 2011, in CSI: Miami (Season 9, Episode 15 “Blood Lust”), it was revealed the killer couple had this condition.
  • The 2011 horror film Intruders contains characters who suffer from folie à deux.
  • In 2012, in Criminal Minds (Season 7, Episode 19 “Heathridge Manor”), it was revealed the killer family had this condition.
  • 2013’s horror game “Slender: The Arrival” centres around the shared hallucination by the main character Lauren, and her friend Kate, of the monster known as “Slender Man”.
  • In 2017, in Chance (Season 2, Episode 9 “A Madness of Two”), it was revealed the villains are having this condition.
  • The Vanished (2020) shows a couple who lost a child continuing to hold on to the delusional thought of their existence.
  • Nine Perfect Strangers (miniseries) shows a couple who lost one of their two children. The couple and the surviving child have shared hallucinations of the dead child.[36]

This page is based on the copyrighted Wikipedia article <https://en.wikipedia.org/wiki/Folie_%C3%A0_deux >; it is used under the Creative Commons Attribution-ShareAlike 3.0 Unported License (CC-BY-SA). You may redistribute it, verbatim or modified, providing that you comply with the terms of the CC-BY-SA.

What are Grandiose Delusions?


Grandiose delusions (GD) – also known as delusions of grandeur or expansive delusions – are a subtype of delusion that occur in patients suffering from a wide range of psychiatric diseases, including two-thirds of patients in manic state of bipolar disorder, half of those with schizophrenia, patients with the grandiose subtype of delusional disorder, and a substantial portion of those with substance abuse disorders.

GDs are characterised by fantastical beliefs that one is famous, omnipotent, wealthy, or otherwise very powerful. The delusions are generally fantastic and typically have a religious, science fictional, or supernatural theme. There is a relative lack of research into GD, in contrast to persecutory delusions and auditory hallucinations. About 10% of healthy people experience grandiose thoughts but do not meet full criteria for a diagnosis of GD.

Signs and Symptoms

According to the DSM-IV-TR diagnostic criteria for delusional disorders, grandiose-type symptoms include exaggerated beliefs of:

  • Self-worth.
  • Power.
  • Knowledge.
  • Identity.
  • Exceptional relationship to a deity or famous person.

For example, a patient who has fictitious beliefs about his or her power or authority may believe himself or herself to be a ruling monarch who deserves to be treated like royalty. There are substantial differences in the degree of grandiosity linked with grandiose delusions in different patients. Some patients believe they are God, the Queen of the United Kingdom, a president’s son, a famous rock star, and some other examples. Others are not as expansive and think they are skilled athletes or great inventors.

Expansive delusions may be maintained by auditory hallucinations, which advise the patient that they are significant, or confabulations, when, for example, the patient gives a thorough description of their coronation or marriage to the king. Grandiose and expansive delusions may also be part of fantastic hallucinosis in which all forms of hallucinations occur.

Positive Functions

Grandiose delusions frequently serve a very positive function by sustaining or increasing their self-esteem. As a result, it is essential to consider the consequences of removing the grandiose delusion on self-esteem when trying to modify the grandiose delusion in therapy. In many instances of grandiosity, it is suitable to go for a fractional rather than a total modification, which permits those elements of the delusion that are central for self-esteem to be preserved. For example, a person who believes they are a senior secret service agent gains a great sense of self-esteem and purpose from this belief, thus until this sense of self-esteem can be provided from elsewhere, it is best not to attempt modification.



Schizophrenia is a mental disorder distinguished by a loss of contact with reality and the occurrence of psychotic behaviours, including hallucinations and delusions (unreal beliefs which endure even when there is contrary evidence). Delusions may include the false and constant idea that the person is being followed or poisoned, or that the person’s thoughts are being broadcast for others to listen to. Delusions in schizophrenia often develop as a response to the individual attempting to explain their hallucinations. Patients who experience recurrent auditory hallucinations can develop the delusion that other people are scheming against them and are dishonest when they say they do not hear the voices that the delusional person believes that he or she hears.

Specifically, grandiose delusions are frequently found in paranoid schizophrenia, in which a person has an extremely exaggerated sense of his or her significance, personality, knowledge, or authority. For example, the person may declare to own a major corporation and kindly offer to write a hospital staff member a check for $5 million if only help them escape from the hospital. Other common grandiose delusions in schizophrenia include religious delusions such as the belief that one is Jesus Christ.

Bipolar Disorder

Refer to Bipolar Disorder.

Bipolar I disorder can lead to severe affective dysregulation, or mood states that sway from exceedingly low (depression) to exceptionally high (mania). In hypomania or mania, some bipolar patients can suffer grandiose delusions. In its most severe manifestation, days without sleep, auditory and other hallucinations, or uncontrollable racing thoughts can reinforce these delusions. In mania, this illness affects emotions and can also lead to impulsivity and disorganised thinking, which can be harnessed to increase their sense of grandiosity. Protecting this delusion can also lead to extreme irritability, paranoia, and fear. Sometimes their anxiety can be so over-blown that they believe others are jealous of them and, thus, undermine their “extraordinary abilities,” persecuting them or even scheming to seize what they already have.

The vast majority of bipolar patients rarely experience delusions. Typically, when experiencing or displaying a stage of heightened excitability called mania, they can experience joy, rage, and other intense emotions that can cycle out of control, along with thoughts or beliefs that are grandiose. Some of these grandiose thoughts can be expressed as strong beliefs that the patient is very rich or famous or has super-human abilities, or can even lead to severe suicidal ideations. In the most severe form, in what was formerly labelled as megalomania, the bipolar patient may hear voices that support these grandiose beliefs. In their delusions, they can believe that they are, for example, a king, a creative genius, or can even exterminate the world’s poverty because of their extreme generosity.


There are two alternative causes for developing grandiose delusions:

  1. Delusion-as-defence: Defence of the mind against lower self-esteem and depression.
  2. Emotion-consistent: Result of exaggerated emotions.

Anatomical Aspects

Grandiose delusions may be related to lesions of the frontal lobe. Temporal lobe lesions have been mainly reported in patients with delusions of persecution and of guilt, while frontal and frontotemporal involvement have been described in patients with grandiose delusions, Cotard’s syndrome, and delusional misidentification syndrome.


Patients with a wide range of mental disorders which disturb brain function experience different kinds of delusions, including grandiose delusions. Grandiose delusions usually occur in patients with syndromes associated with secondary mania, such as Huntington’s disease, Parkinson’s disease, and Wilson’s disease. Secondary mania has also been caused by substances such as L-DOPA and isoniazid which modify the monoaminergic neurotransmitter function. Vitamin B12 deficiency, uraemia, hyperthyroidism as well as the carcinoid syndrome have been found to cause secondary mania, and thus grandiose delusions.

In diagnosing delusions, the MacArthur-Maudsley Assessment of Delusions Schedule is used to assess the patient


In patients suffering from schizophrenia, grandiose and religious delusions are found to be the least susceptible to cognitive behavioural interventions. Cognitive behavioural intervention is a form of psychological therapy, initially used for depression, but currently used for a variety of different mental disorders, in hope of providing relief from distress and disability. During therapy, grandiose delusions were linked to patients’ underlying beliefs by using inference chaining. Some examples of interventions performed to improve the patient’s state were focus on specific themes, clarification of patient’s neologisms, and thought linkage. During thought linkage, the patient is asked repeatedly by the therapist to explain their jumps in thought from one subject to a completely different one.

Patients suffering from mental disorders that experience grandiose delusions have been found to have a lower risk of having suicidal thoughts and attempts.


In researching over 1000 individuals of a vast range of backgrounds, Stompe and colleagues (2006) found that grandiosity remains as the second most common delusion after persecutory delusions. A variation in the occurrence of grandiosity delusions in schizophrenic patients across cultures has also been observed. In research done by Appelbaum et al. it has been found that GDs appeared more commonly in patients with bipolar disorder (59%) than in patients with schizophrenia (49%), followed by presence in substance misuse disorder patients (30%) and depressed patients (21%).

A relationship has been claimed between the age of onset of bipolar disorder and the occurrence of GDs. According to Carlson et al. (2000), grandiose delusions appeared in 74% of the patients who were 21 or younger at the time of the onset, while they occurred only in 40% of individuals 30 years or older at the time of the onset.


Research suggests that the severity of the delusions of grandeur is directly related to a higher self-esteem in individuals and inversely related to any individual’s severity of depression and negative self-evaluations. Lucas et al. (1962) found that there is no significant gender difference in the establishment of grandiose delusion. However, there is a claim that ‘the particular content of Grandiose delusions’ may be variable across both genders. Also, it has been noted that the presence of GDs in people with at least grammar or high school education was greater than lesser educated persons. Similarly, the presence of grandiose delusions in individuals who are the eldest is greater than in individuals who are the youngest of their siblings.

Book: Delusions and Delusion Disorder

Book Title:

Delusions and Delusional Disorder: The Power to Heal Someone from Mental Disorder.

Mental Health – Psychosis Symptoms and What To Do.

Author(s): Jon Carson.

Year: 2021.

Edition: First (1st).

Publisher: Independently Published.

Type(s): Paperback and Kindle.


Delusional disorder, recently called paranoid disorder, is a kind of genuine mental illness called a psychotic disorder. Individuals who have it can’t determine what’s genuine based on what is envisioned. Delusions are the fundamental manifestation of delusional disorder. They are relentless convictions in something that is not correct or dependent on the real world.

Individuals with the delusional disorder frequently can proceed to mingle and work regularly, aside from the subject of their dream, and by and large, do not carry on in a clearly odd or strange way.

The study material provides summarised various answers to the questions that are likely to be the in minds of readers. This covers:

  • Vivid introduction delusional disorder.
  • Various types of delusion.
  • What are the indications of delusional disorder?
  • What are the causes and dangerous elements of delusional disorder?
  • Could pressure cause delusions?
  • How is a delusional disorder diagnosed?
  • Treatment of delusional disorder treated.
  • What are the intricacies of delusion disorder?
  • What’s the standpoint for individuals with the delusional disorder?
  • Can the delusional disorder be forestalled?
  • Supportive activities when somebody who has a psychological sickness is encountering hallucinations, delusions, or paranoia.