ICD-116A24	DELUSIONAL DISORDER Delusional disorder
ICD-10F22	Persistent delusional disorders
DSM-5-TRF22	Delusional Disorder

1. Definition and nosology

Delusional disorder (ICD-11: 6A24 Delusional Disorder; DSM-5-TR: F22) — a psychotic disorder in which one or several delusions predominate for at least one month, without meeting the full criteria for schizophrenia. The patient's general behavior and functional level remain relatively intact except for the delusional state.

2. History

• Kraepelin (1899) — “paranoia” — systematized delusion without hallucinations.
• Esquirol J.E. (1810s) — the term “monomania”; Kahlbaum K. (1863) and Krafft-Ebing R. — the clinical description of paranoia.
• DSM-III-R (1987) — “Delusional Disorder” established as an official diagnosis; continuation of Kraepelin's paranoia concept.
• ICD-11 (2019): Bizarre delusions also permitted (in ICD-10 only non-bizarre); induced delusion (folie à deux) integrated as separate subtype.

3. Epidemiology

• Lifetime prevalence: ~0.2% (Perälä 2007).
• Onset: middle age (35–55 years), significantly later than schizophrenia.
• Gender: approximately equal; differences in some subtypes (erotomania in women).
• Comorbidity: depression, anxiety, social isolation; high suicide risk.

4. Aetiology and pathogenesis

• Genetic load is less than in schizophrenia; however, family history shows increased density of paranoid personality and psychotic disorder.
• Sensory deprivation (hearing impairment) — increases risk of paranoid delusions in the elderly.
• Social isolation, migration, language barriers — risk factors.
• Neurobiological — dopaminergic dysregulation, but more localized than in schizophrenia; increased striatal dopamine synthesis in some studies (Howes O.D. reviews).

5. Clinical features

Subtypes (by delusional content)

• Persecutory (persecutor): Most frequent — being followed by others, harm planned.
• Jealousy (Othello syndrome): delusion about partner's betrayal; high criminal risk.
• Erotomanic (Clérambault syndrome): belief that another person (usually of higher status) loves the patient.
• Grandiosity: special ability, talent, discovery, religious mission.
• Somatic: Belief of parasites in the body (Ekbom syndrome), emitting odor, deformity.
• Mixed and nonspecific.

Functional maintenance

Outside the delusion, the patient's general behavior, affect, cognitive functions are relatively preserved; work and relationships can continue as long as they do not touch on delusion content.

6. Diagnosis

6.1 Unified diagnostic criteria (DSM-5-TR · ICD-11)

A. One or more delusions persisting: ICD-11 — at least 3 months (usually much longer), DSM-5-TR — at least 1 month.

B. Schizophrenia failing to meet criterion A (delusion is the sole or dominant symptom; possible when hallucinations are minimal and related to delusional content).

C. Functional preservation without direct effect of delusion; behavior not bizarre.

D. If an affective episode is present, it occurs during a small portion of the delusional period.

E. Exclusion of substance or organic cause.

6.2 Source-specific clarifications

• ICD-11: Permission for bizarre delusions (also removed prohibition in DSM-5-TR); induced delusion (folie à deux) integrated into 6A24.
• DSM-5-TR: Subtype qualifiers (erotomanic, grandiose, jealous, persecutory, somatic, mixed, unspecified); ‘bizarre type’ additional qualifier.

6.3 Diagnostic algorithm

1. Clinical interview (general and especially delusional content).
2. Relative/friend interview – premorbid function, onset of delusions.
3. SCID-5 / MINI; PANSS / BPRS Positive Symptom Subscale.
4. Medical and neurological examination.
5. Toxicology screening; sensor (hearing, vision) test — mandatory in elderly.
6. Brain MRI (at first episode).
7. Comorbid depression and suicide risk assessment.

6.4 Differential diagnosis

7. Examination and assessment

• PANSS / BPRS positive symptom subscale; structured documentation of concrete delusion content.
• Hearing and vision test (mandatory in the elderly).
• Laboratory: complete blood count, thyroid, B12, liver, glucose, toxicology screening, syphilis, HIV, ANA (lupus), ceruloplasmin (Wilson).
• Brain MRI — first episode, atypical clinical picture, elderly patient.
• Assessment of suicide and violence risk (C-SSRS, especially in jealousy delusions).

8. Treatment

1. Atypical antipsychotic at low dose (risperidone 1–3 mg, olanzapine 5–10 mg, aripiprazole 5–15 mg) — first-line. Evidence base is less than for schizophrenia; patient adherence is problematic (due to delusional content).
2. Pimozide was historically considered superior in erotomania and somatic delusions (Munro A. studies), but in modern practice it is used less often than the atypicals (QTc, EPS).
3. Psychotherapy — supportive therapy, building therapeutic alliance; CBT (non-confrontational work with delusional content, exploring alternative explanations).
4. Comorbid depression — SSRI.
5. Violence or suicide risk (especially delusions of jealousy) — hospitalisation and involuntary treatment within the legal framework.
6. Sensory disorder — hearing devices or vision correction – sometimes have profound effect in elderly paranoid delusions.
7. Social support — reduction of isolation; family psychoeducation.

Source-specific specifications

• NICE CG178 — no separate algorithm for delusional disorder; general psychosis principles.
• APA 2021 — antipsychotic first-line; insight and adherence difficulty emphasized.
• Munro A. reviews (Cambridge Univ Press 1999) — subtype-specific clinical guidance.

Treatment methods

1. Non-confrontational CBT — Explore alternative explanations and evidence with the patient without openly denying the delusion content. Birchwood M., Trower P. studies — effective in schizophrenia and delusional disorder.
2. Supportive therapy and therapeutic alliance — Establish long-term trusting relationship with the patient; strengthening of adherence.
3. PANSS positive symptom subscale — Standardized assessment of delusion severity and interference degree.
4. Columbia-Suicide Severity Rating Scale (C-SSRS) — Suicide risk — particularly in jealousy and persecutory delusions, violence risk additionally assessed.

9. Prognosis

• Prognosis is better than schizophrenia — functional preservation, late onset.
• Adherence is the main limitation.
• Jealousy and somatic delusions relatively more difficult to treat.
• In older adults, improvement with sensory correction is possible.
• Monitoring — antipsychotic side effects, delusion severity, violence and suicide risk.

10. Myths and misconceptions

Myth 1: “The patient must be convinced of the falseness of their delusion”

Clinical logic: open confrontation disrupts therapeutic alliance and may reinforce delusions; the patient arrives at an explanation of his own: the doctor is against me too.

Evidence: Birchwood and Trower CBT approaches — a non-confrontational approach allowing the patient to explore alternative explanations themselves is effective.

Myth 2: “Delusional disorder can only be treated with psychotherapy, antipsychotics are unnecessary”

Evidence: An antipsychotic is the first-line pharmacotherapy; psychotherapy alone is insufficient. APA 2021, NICE CG178.

Myth 3: “Erotomania is only a female disorder, absent in males”

Evidence: Erotomania occurs in both sexes; higher risk of violence reported in male patients (Menzies R.P. et al. Br J Psychiatry 1995).

Myth 4: “Delusional jealousy is a sign of ‘great love’, not a medical condition”

Evidence: Othello syndrome is a clinical psychotic condition, high risk of violence and homicide against partner; requires active medical intervention.

Myth 5: “Paranoid delusions in the elderly are ‘normal aging’”

Evidence: In older adults, paranoid delusions are often a marker for sensory deprivation (auditory impairment) or early dementia; it can be treatable. Hearing aids or vision correction sometimes yield significant improvement.

Myth 6: “Exorcism or religious intervention cures delusions”

Evidence: Psychotic symptoms are neurobiological; antipsychotic treatment delayed.

Myth 7: The delusional patient must be isolated — social contact is harmful

Evidence: Social isolation, conversely, strengthens psychosis; social support and psychotherapy are recommended.

11. Sources

1. WHO. ICD-11. 6A24 Delusional disorder. 2024.
2. APA. DSM-5-TR. 2022.
3. NICE CG178. Psychosis and schizophrenia in adults. 2014/2019.
4. APA. Practice Guideline for Schizophrenia, 3rd ed. 2021.
5. Munro A. Delusional Disorder: Paranoia and Related Illnesses. Cambridge University Press; 1999.
6. Perälä J. et al. Arch Gen Psychiatry 2007;64(1):19–28.
7. Menzies R.P., Fedoroff J.P., Green C.M., Isaacson K. Prediction of dangerous behaviour in male erotomania. Br J Psychiatry 1995;166(4):529–536.
8. Howes O.D., Kapur S. Schizophr Bull 2009;35(3):549–562.
9. Trower P., Birchwood M., Meaden A. et al. Cognitive therapy for command hallucinations: randomised controlled trial. Br J Psychiatry 2004;184:312–320.