Delusional disorder


Delusional disorders are clinical manifestations during which the patient does not control the reality of things and has the conviction to hold the truth.

Previously, we used the term paranoia (Greek origin which means “side thinking”).

This misinterpretation of reality is confirmed by the patient’s entourage during the medical examination.

Despite the coherence of the ideas and the unreality of the facts, it is impossible to reason with the patient.

Delusional disorders should not be confused with:

  • hallucinations found in schizophrenic patients (psychiatric illness characterized by psychoses).
  • delirium (also called acute confusional episode) which is characterized by an incoherence of ideas, and an alteration of consciousness.


In the late 19th century, German psychiatrists such as Kraepelin included delusional disorder in the definition of paraphrenia, a mental disorder characterized by paranoid delusion without hallucinations.

While Kraepelin excludes hallucinations from the criteria, Bleuer considers schizophrenia to be a paranoid form of dementia praecox associated with hallucinations.

Over the years, Canadian psychiatrists have proposed a paranoid spectrum with several profiles: personality disorders (borderline, avoidant), delusional disorders (persecution, megalomaniac, jealousy, etc.), psychotic disorders, paraphrenia (paranoia, paranoid psychosis), organic disorders ( substance abuse, Alzheimer’s, delirium)

Is delirium common in the elderly?

The lifetime prevalence is 0.03% (1% for schizophrenia), with a majority of men suffering from paranoid delusional disorder.

Delusional disorder usually occurs between the ages of 35 and 45.

It is difficult to assess the frequency in the elderly because, on the one hand, the number of studies is limited and, on the other hand, the concept of an elderly person varies from one study to another.

However, it is estimated that 4% of individuals aged 65 and over living in the community have ideas of persecution (see below the different themes of delirium).

The prevalence would be 10% in individuals aged 65 and over admitted to hospital.

Another study reports a 7% frequency of delusions among people aged 85 and over.

What are the recurring themes of delusional disorder?

Delusional themes represent the basis on which delusions develop.

These themes are those of persecution, prejudice, intrusion, jealousy, megalomania… They are centred on his person, his body, his family, his neighbours and his possessions.


This theme is the most common. The subject is convinced of being persecuted, watched or threatened, convinced of the existence of a conspiracy. Ideas of persecution may be accompanied by attacks of death anxiety with fear of imminent danger or annihilation. Unlike the delusion of schizophrenia, the persecutory delusional theme is clear, with some logic.


The patient is afraid of losing his property, his health and his reputation. The patient is sad and worried. He criticizes those around him. He thinks that someone is breaking into his house and that he risks losing his property. He isolates himself and flees his neighborhood.

ruin, theft

The patient is convinced of being ruined, robbed, abandoned by his loved one.


The theme relates to the conviction of his wife’s infidelities . Delirium develops from the misinterpretation and amplification of trivial facts. The jealous person can hire a detective to follow them. This type of delirium is often linked to alcohol consumption.


The patient thinks he is being ‘persecuted’ by his organs or living organisms. This is the case, for example, of Eckbom syndrome, a condition during which the patient is convinced that he is infested by small animals (insects, parasites) which develop on or in the skin. Many of these patients suffer from manic depression or paranoid delirium. The patient is therefore convinced that he is suffering from a serious illness, but he can also be convinced that he is giving off bad smells.


The patient has an exaggerated idea of ​​his own worth, power and knowledge. He thinks he has an exceptional relationship with a famous person. He thinks he has been appointed to accomplish a great mission. This theme is frequent in delusional manias. This megalomania is distinct from paranoid schizophrenia, where megalomania is associated with schizophrenic symptoms.


The patient believes he is loved by someone, usually on a higher level. It is above all an idealized and romantic love.

Charles Bonnet Syndrome

It occurs after an ophthalmological intervention (caused for example by a sudden ocular occlusion), or in patients suffering from retinopathy, cataracts, or when the associative visual area is affected (in the case of dementia). It is characterized by visual, colorful hallucinations rich in detail depicting characters or animals that are not threatening. The triggering factors are a drop in the level of consciousness or low ambient light.

Madness for two

Delusional syndrome involving a couple (husband-wife; father-daughter, mother-daughter) during which one of the two partners, schizophrenic and of a dominant character, transmits his delirium to his partner with a physical (or intellectual) handicap and a passive personality -dependent. Sometimes the passive-dependent partner is also psychotic (this is called simultaneous insanity). The separation of the two people is generally necessary, which can lead to the disappearance of the delirium in the second person, while the first will be treated with antipsychotics.

How does the doctor diagnose delirium?

The physician relies on diagnostic criteria from the American psychiatry manual DSM IV (used in North America) and the International Statistical Classification of Diseases and Related Health Problems, 10th revision (ICD-10, World Health Organization). Health), mostly used in Europe.

Factors that increase the risk of delirium

Cognitive decline appears to be the primary risk factor.

There are also biographical, social or psychological factors that favor the appearance of delirium:

  • Family history of schizophrenia
  • Avoidant personality disorder, borderline, paranoid.
  • Paranoid or schizoid personality (personality that tends to withdraw into itself).
  • Isolation and loneliness (single, widowhood).
  • The lack of social fabric and withdrawal into oneself (schizoid personality).
  • The attitude of those around you.
  • The feeling of insecurity.
  • A low socio-economic level.
  • A low level of education.
  • Sensory deficits (auditory and visual) that lead to misinterpretations
  • Alterations associated with physical illnesses (hypoglycemia due to diabetes, high fever, electrolyte disturbances, lupus, cerebrovascular disorders)

Aging delirium versus late-onset delirium

There are two forms of delirium:

1. Delirium diagnosed in adulthood and persisting into old age. The intensity of the delirium tends to fade.

2. Delirium that appears in old age (or late-onset delirium), i.e. after 65 years. The onset is insidious and is sometimes accompanied by hallucinations. This form may or may not be associated with a brain condition such as  Alzheimer’s disease,  vascular dementia, depression,  bipolar disorder.

At advanced age, doctors therefore distinguish functional delusions from delusions caused by a neurological disease.

In summary , delusional disorders are classified with the psychotic disorders seen in schizophrenia:

– Paranoid, disorganized, catatonic, undifferentiated schizophrenia…

– Brief psychotic disorder.

– Shared psychotic disorder (madness for two).

– Psychotic disorder secondary to a general medical condition.

– Delusional disorders.

– Persistent delusional disorders (late paraphrenia*, involutional paranoia**): this encompasses all conditions involving delirium accompanied by hallucinations, in particular auditory.

Paraphrenia*: imaginative delirium organized around themes of greatness, persecution, melancholy, mysticism…

Paranoia of involution**: delusion of claim appearing late.

The doctor must take into account the personality of the patient, his past, his social and affective environment and somatic factors.

The doctor questions the patient and his entourage in order to determine the age at which the symptoms appeared.

It captures the patient’s personality, mood, medical history, and identifies delusional themes.

Neurological examination can determine if a brain condition is causing the delirium.

Delirium Assessment

Various symptoms can be associated with delirium;

  • Hypervigilance. The person has a misinterpretation of the observed facts that he observes in detail.
  • Personal interpretation. He systematically interprets his observations in an unambiguous sense that confirms his delusional theory.
  • Mistrust. He responds in an irritated manner when asked about his delirious themes.
  • Auditory or visual hallucinations. They are rare in delusional disorders.
  • Unwanted behaviors. The patient who feels provoked may respond defensively, fearfully, or aggressively.
  • Grandiosity. The patient places excessive personal importance on herself. He becomes easily hostile, feeling persecuted by envious people who want to discredit him.
  • Depressive affect. Some patients burst into tears when they meet a person receptive to their sufferings.

Diagnostic tools

There is no instrument that specifically assesses delirium in the elderly. There is, for example, the scale for evaluating psychoses in adults (example PDI) or the psychological and behavioral disorders of dementia (example:  the neuropsychiatric inventory of dementia).

Finally, the Behavioral Pathologic Rating Scale for Alzheimer’s disease is a behavioral disorder rating scale that describes the different forms of delirium in Alzheimer’s disease.

In the Behavioral Pathologic Rating Scale for Alzheimer’s disease, the different forms of delirium are classified by theme (theft, imposter syndrome, etc.):

1. The patient believes that he has had things stolen (frequency = 18% to 43%).

Probable explanation: the patient no longer remembers the location of his personal objects, and will blame a loved one for their disappearance. In serious forms, he is convinced that someone is entering his home with the aim of hiding or stealing objects.

2. The patient believes he is living in a home that is not his.

The patient does not remember or recognize his home. He may end up leaving it to return « home » (this is the phenomenon of wandering).

3. The spouse (or the relative in charge of the patient) is perceived as an impostor.

The patient no longer recognizes his loved one. He may also consider his caregiver as an impostor, which results in a reaction of mistrust, even violence. In some cases, the patient is convinced that familiar people have been replaced by identical look-alikes: this is Capgras syndrome. These identification disorders are stressful for those around them because they are difficult to manage.

4. A feeling of abandonment (frequency = 3% to 18%).

The patient is convinced that he has been abandoned, that he will be placed in an institute, and that a plot is being organized for this purpose. This feeling stems from the fact that he realizes the burden he represents for those around him because he retains a certain awareness of his condition. Relatives feel guilty for this feeling of abandonment experienced by the patient.

5. A feeling of infidelity (frequency = 1% to 9%).

This feeling mainly concerns the spouse or caregivers.

Although the diagnosis of delirium is sometimes difficult in a person with dementia  (indeed people with dementia already have a disorder of ideation and confusion), it is possible with some experience to tell the difference between delirium and dementia. Indeed, delirium is usually accompanied by:

  • a sudden onset of symptoms;
  • a decrease or increase in alertness in the patient already presenting with dementia, or a marked fluctuation in symptoms;
  • visual hallucinations accompanied by agitation;
  • impaired psychomotor activity;
  • language disorders (slurred speech, slowing or speeding up of speech);
  • of tremors.

Once the diagnosis of delirium is made, the choice of treatment will depend on identifying the cause. These causes are many and include:

  • medication side effects;
  • malnutrition;
  • an infection;
  • cerebral pathologies (eg, subdural hematomas);
  • endocrine disorders (eg hyperthyroidism);
  • metabolic diseases (eg certain kidney or liver conditions);
  • patient environmental factors;
  • hypoxia caused by pneumonia, congestive heart failure or sleep apnea;
  • urinary retention or fecal impaction (accumulation of feces).

Delirium occurring in adulthood (before age 65)

It encompasses paranoid states and psychotic disorders diagnosed in adults with schizophrenia and which persist into old age. These disorders become less intense as the person ages. An estimated 13% of people with schizophrenia (usually diagnosed in their 20s) show initial symptoms after their 40s, and only 3% after their 60s. In this category of patients, the negative symptoms (eg withdrawal, indifference) tend to persist while the delusional manifestations and hallucinations, mainly auditory, considered as positive symptoms, tend to diminish.

Late-onset delirium (after age 65)

Late-onset delusions are delusions appearing after age 65.

These delusions are caused, for example, by a sensory deficit (we then speak of functional delirium), a mental illness (depression, dementia) or cerebrovascular disease.

Evaluation of cognitive functions, questioning of the family and a brain examination (MRI) make it possible to know if a dementia (dementia of the Alzheimer type,  vascular dementia,  dementia with Lewy bodies) is at the origin of a delirium.

Functional delusions

They develop in a lasting mode and are caused by:
– a stressful situation (death, move, entry into a medical institution, etc.);
– a sensory, cognitive deficit, affecting communication and relational life. This is the Charles Bonnet syndrome (see above), the Eckbom syndrome (see above), the paranoia of the deaf (the patient, suffering from severe hearing loss, is wary and withdraws into himself. He has auditory hallucinations).

Delirium associated with depression

Depression in old age is often accompanied by delirium: this is called delusional depression. 40% of hospitalized patients suffer from delusional depression. The themes of the delirium relate to ruin, guilt and persecution.

Delusional depression may or may not be melancholic. In cases of melancholy, patients close themselves in the past, with representations or apparitions.

In certain cases of delusional depression, the patient, hypochondriacal, feels his organs putrefying and destroying himself, thinks he has an incurable disease: this is Cotard’s syndrome.

Delusional disorders associated with Alzheimer’s disease

Delusional disorders at the beginning of the dementia stage revolve mainly around forgetfulness.

The frequency of delusions in people with dementia is between 10% and 73% depending on the population studied. About a third of patients with probable Alzheimer’s disease suffer from delusions, and are considered to be at risk for physical aggression. According to one study, 80% of participants with high levels of physical aggression (>1 episode/month) also suffered from delusions.

Delusions in the early stage are linked to memory loss. They lead to ideas of displacement and theft of objects, intrusion into the home, spoliation, infidelity and jealousy (15% of cases). They may be accompanied by aggressiveness in a person with a psychiatric history. Late companion delirium is typical of dementia. The subject reconstructs a new reality where people from the past or fantasy come to keep him company.

As the disease progresses, the delusions aim to fill the growing void caused by the memory loss, and draw on the remnants of memories still intact in the patient.

We observe delusions of identification during which the patient, suffering from gnosic, mnesic and judgment disorders, perceives people or objects in a distorted way, resulting in situations that are poorly experienced by those around him.

Thus, the spouse can be taken for example for an impostor (this is Capgras syndrome), or the patient is convinced that people take on the appearance of others (this is Fregoli syndrome), suffers from ‘a disorder of self-identification in the mirror (prosopagnosia), has the conviction of the presence of people in the house, the certainty that the television characters are in the room and steal thoughts, etc. These disorders cause anxiety and/or behavioral disorders (agitation, wandering).

Dementia secondary to Parkinson’s disease

Dementia secondary to Parkinson’s disease occurs after at least 5 years of evolution. Hallucinations are found in three quarters of cases, and are essentially visual.

Delusions associated with cerebrovascular  disease

Mini-lesions increase the risk of delusional disorders, accompanied by hallucinations evoking the presence of animals and people.

Delirium and hallucinations

Although delirium should not be confused with hallucinations, a person suffering from delirium can have hallucinations, but these are not predominant.

Hallucinations interfere with the patient’s ability to understand the outside world. This phenomenon can alter their ability to perform activities of daily living and can affect their relationship with caregivers. The frequency of hallucinations in people with dementia ranges from 12 to 49%.

Visual hallucinations are the most common (up to 30% of patients with dementia), and they are more common in moderate dementia than in mild or severe dementia.

Auditory hallucinations are present in 10% of dementia cases.

Other forms of hallucinations, tactile and olfactory, are rare.

A common type of visual hallucination involves observing the presence of certain people in one’s home, when in fact they are not there. In the case of Lewy* dementia, the interpretation disorders are based above all on gnosic deficits, and to a lesser extent on mnesic disorders and sensory perception defects. The most frequently observed gnosic deficits are prosopagnosia (the patient does not recognize his relatives; 12% of cases), self-agnosia (4% of cases), intrusion of people into the patient’s life ( 6% of cases), or the ghost companion syndrome (the patient is convinced that a person is hiding in his home (17% of cases). These hallucinations sometimes require treatment when they are a source of stress. This treatment depends on the etiology.

Dementia with Lewy bodies* is characterized by the presence of hallucinations in 60% of cases and this at an early stage (living or deceased pets or familiar characters.

There is an association between decreased visual acuity and hallucinations (see Bonnet syndrome above). Indeed, a significant percentage of people with dementia have a visual deficit (eg visual agnosia characterized by difficulty recognizing faces or objects), and many experience difficulty in contrast perception, especially in low frequencies. Indeed, the line of demarcation between the areas of shadow and light is blurred in demented patients, which partly explains the high rate of identification disorders and visual hallucinations.

To prevent these hallucinations, the eyesight of patients with dementia must be assessed and home lighting improved.

The differential diagnosis

The doctor will have to rule out the diagnosis of mental confusion which can a priori be confused with delirium.

Indeed, during a confusional episode, the patient has convictions that are erroneous and persistent.

In mental confusion, the mode of onset is abrupt, the disturbances are fluctuating and alertness is impaired.

To eliminate any doubt, the doctor will have to determine a somatic, iatrogenic or toxic cause.

Delusional states can be the consequence of Lewy body dementia. In this case, they precede cognitive decline, which can lead the doctor to misdiagnose.

The presence of motor disorders (akinesia), the occurrence of falls, a cerebral examination and hypersensitivity to antipsychotics*, will guide the doctor towards the diagnosis of this form of dementia. * The doctor usually prescribes an  antipsychotic (or neuroleptic)  to patients with psychosis. If this psychosis is caused by dementia with Lewy bodies, the drug will cause side effects that will aggravate motor disorders, one of the main symptoms of this form of dementia.


If the delirium is associated with another mental disorder, it must be treated first.

The ideal treatment includes:

  • an antidepressant (of the selective serotonin reuptake inhibitor type) in the case of major depression with psychotic symptoms.
  • an antipsychotic (eg risperidone or olanzapine) to reduce anxiety, restlessness and sleep disturbance caused by delirium if the latter is part of schizophrenia.
  • valproic acid or lithium in the case of a manic episode, with a benzodiazepine.

In the case of delusions associated with dementia (Alzheimer’s disease or dementia with Lewy bodies), acetylcholinesterase inhibitors (i.e. donepezil, rivastigmine or galantamine) would reduce the agitations related to delirium . The use of antipsychotics is possible, provided that they are prescribed at low doses (1 mg/day for risperidone, 5 mg/day for olanzapine) and over a short period (two weeks maximum). Indeed, elderly patients suffering from dementia and receiving an antipsychotic have an increased risk of stroke. Antipsychotics are not recommended in dementia with Lewy bodies because they aggravate motor disorders.

A non-pharmacological approach will be combined with drug treatment.

Thus psychotherapy sessions will be offered to gain the patient’s trust, so that he can express without hesitation what worries him.

The psychotherapist will have to accept the delusional comments of the patient, without adhering to them.

The care team can also improve the relationship between the patient and the family and correct any factors that promote these disorders (correction of a sensory handicap, promote social relations, reduce the feeling of insecurity, etc.).

A non-pharmacological approach will be combined with drug treatment.

Thus psychotherapy sessions will be offered to gain the patient’s trust, so that he can express without hesitation what worries him.

The psychotherapist will have to accept the delusional comments of the patient, without adhering to them.

The healthcare team can also improve the relationship between the patient and the family and correct any factors that favor these disorders (sensory handicap, lack of social relationships, feeling of insecurity, etc.).

Clinical case

A woman was treated for decades for bipolar 1 disorder with lithium. His treatment was stopped because relapses were frequent. In addition, lithium caused hypothyroidism in her.

Around the age of 70, she presented significant depressive symptoms accompanied by delusional thoughts (notably delusion of persecution).

Doctors diagnose delirious melancholy.

She is being treated with an antidepressant combined with an antipsychotic.

Her treatment is difficult because, on the one hand, she is convinced that the drugs are prescribed to aggravate her physical condition and, on the other hand, the food is « poisoned » by drugs.

His mental and physical condition deteriorated: social withdrawal, repeated falls, incontinence. She refuses to take her antidepressant.

Delusional disorders with hypochondria develop: the patient thinks that her liver is no longer in her body and that she cannot therefore absorb the drugs that the doctors want to give her.

Treatment with electroconvulsive therapy (ECT) is indicated by doctors given his poor nutritional status. The doctors obtain the written consent of one of the children as required by French law (in this case, the doctors could not obtain the patient’s consent because of her condition).

After about ten sessions, the patient shows signs of improvement: improvement in contacts, reduction in the delirium of persecution.

An anti-depressant and a mood modulator are prescribed.

This time the patient agrees to these treatments.

Her delusional disorders decrease in intensity, and her condition improves: she talks with the nursing staff, reads, washes herself, moves, etc. Her mood is stable.

She will go home and get help at home.