Delusional Disorder
Delusional disorder is characterised by non-bizarre delusions persisting for ≥1 month without other prominent psychotic features. Functioning is relatively preserved.
Key Facts
Non-bizarre delusions (plausible real-life situations) persisting ≥1 month — key diagnostic feature Subtypes: Persecutory (most common ~50%), erotomanic, grandiose, jealous (Othello syndrome), somatic Prevalence ~0.02-0.03%; mean onset age 40-50 years; slight female predominance Functioning is relatively preserved — no prominent negative symptoms, thought disorder, or hallucinations First-line: Antipsychotic (risperidone 1-4mg, olanzapine 5-15mg) ± CBT — managed under NICE CG178 Jealous type carries significant risk of violence towards partner — urgent risk assessment required De Clérambault syndrome (erotomania): Delusion that a person of higher status is in love with the patient — risk of stalking Distinguished from schizophrenia by absence of bizarre delusions, prominent hallucinations, thought disorder, and negative symptoms
Overview
Key Facts
Delusional disorder involves fixed, systematised, non-bizarre delusions without the broader psychotic features of schizophrenia. Behaviour outside the delusional system is not markedly bizarre.
Epidemiology
Lifetime prevalence is approximately 0.02-0.03%. Mean onset is 40-50 years, later than schizophrenia. Persecutory subtype accounts for ~50% of cases. Slight female predominance.
Aetiology
- Neurobiological: Dopaminergic dysfunction in limbic system, though less pronounced than schizophrenia
- Psychological: Attribution biases, jumping-to-conclusions reasoning, social isolation, sensory impairment (hearing/vision loss in elderly)
- Genetic: Some familial association with schizophrenia spectrum disorders
- Social: Immigration, social adversity, loneliness
Pathophysiology
- Abnormal salience attribution — brain assigns excessive significance to neutral stimuli
- Jumping-to-conclusions bias — less evidence required before forming beliefs
- Theory of mind deficits may promote paranoid ideation
- Minimal structural brain changes compared to schizophrenia
Clinical Presentation
Subtypes
- Persecutory: Being conspired against, followed, poisoned (most common)
- Erotomanic: Another person (usually higher status) is in love with the patient
- Grandiose: Exceptional talent, power, or special relationship
- Jealous (Othello syndrome): Unfounded conviction of partner's infidelity
- Somatic: Body function abnormality (emitting odour, parasites, deformity)
Key Clinical Features
- Delusions are systematised and logically developed
- Affect appropriate to delusional content
- No prominent hallucinations, thought disorder, or negative symptoms
- Relatively preserved functioning outside delusional system
Red Flags
- Jealous type with aggression towards partner — significant violence risk
- Persecutory delusions with retaliation plans — forensic risk
- Erotomania with stalking behaviour — legal and safety implications
- Somatic type with repeated inappropriate medical/surgical consultations
Differential Diagnosis
| Diagnosis | Key Features | Investigation |
|---|---|---|
| Schizophrenia | Bizarre delusions, hallucinations, thought disorder, negative symptoms | MSE, longitudinal history |
| Bipolar mania | Grandiose delusions during mood episode, episodic | Mood history, collateral |
| Psychotic depression | Mood-congruent delusions during severe depression | PHQ-9, MSE |
| OCD | Overvalued ideas with insight, ego-dystonic | Y-BOCS |
| Body dysmorphic disorder | Preoccupation with perceived physical defect | Clinical assessment |
| Organic psychosis | Medical/neurological cause | MRI, bloods, drug screen |
Diagnosis / Investigation
Bedside
- MSE: Delusional content, systematisation, insight assessment
- Risk assessment: Particularly jealous and persecutory types
- Collateral history: Patient may present convincing narrative
Bloods
- TFTs, FBC, U&Es, LFTs, calcium, B12: Exclude organic causes
- Urine drug screen: Exclude substance-induced psychosis
Special Tests
- MRI brain: Consider in late-onset presentations
- Audiometry/vision testing: Sensory impairment as contributing factor
- Cognitive assessment: Exclude dementia in elderly
Management
Non-pharmacological
- Build therapeutic alliance without colluding with or directly challenging delusion
- CBT: Guided discovery to examine evidence for/against beliefs
- Social interventions to address isolation
Pharmacological
- Antipsychotics (often partially effective; patients frequently reluctant):
- Risperidone 1-4mg OD or olanzapine 5-15mg OD
- Lower doses than schizophrenia may suffice
- Trial ≥6-8 weeks at adequate dose
- SSRIs: If comorbid depression or somatic subtype
- Managed under NICE CG178 (psychosis and schizophrenia)
Referral Criteria
- All suspected cases — psychiatric assessment
- Jealous type with partner at risk — urgent safeguarding
- Stalking behaviour — forensic psychiatry
- Failed outpatient treatment — inpatient assessment
Prognosis
- Chronic course: ~50% persistent delusions; ~20% full remission; ~30% partial remission
- Better prognosis: Female sex, acute onset, shorter duration, non-paranoid subtype
- Jealous type: One of the most dangerous psychiatric presentations — significant partner violence risk
- Functional outcome: Generally better than schizophrenia
- Treatment engagement: Poor — many patients lack insight
Other Relevant Information
Delusional Disorder vs Schizophrenia
| Feature | Delusional Disorder | Schizophrenia |
|---|---|---|
| Delusion type | Non-bizarre | Often bizarre |
| Hallucinations | Minimal/absent | Prominent |
| Thought disorder | Absent | Common |
| Negative symptoms | Absent | Common |
| Functioning | Relatively preserved | Often impaired |
| Age of onset | 40-50 years | 18-30 years |
| Prognosis | Better | Worse |