Delusional disorder

Single/circumscribed non-bizarre delusion, preserved function outside it

UrgentReview due

Compare (8)

At a glance

High-risk causes: 5
Core tests: 3
Immediate actions: 6
Related differentials: 8

Safety snapshot

Watch forJealous/persecutory/erotomanic violence riskstalkingtreatment refusalStalkingviolencesevere treatment refusal

Presentation hinge

Often fixed, systematised, accompanied by hallucinations, thought disorder, or negative symptoms.

Separates the Delusions / Paranoia / Thought Interference / Command Phenomena group. It is not specific to Delusional disorder.

Points for this presentation

Applies to the Delusions / Paranoia / Thought Interference / Command Phenomena group — not specific to Delusional disorder

In older or medically unwell patients, assume delirium until proved otherwise
Cannabis and stimulants can closely mimic primary psychosis
Reassess once partially cleared
Escalate early to medical/neurology review if red flags are present

Clinical review

Rows marked “Whole group”: Applies to the Delusions / Paranoia / Thought Interference / Command Phenomena group — not specific to Delusional disorder

Why it fits

Single/circumscribed non-bizarre delusion, preserved function outside it

Key features2 features

Fixed non-bizarre delusion with preserved function
Inattention and fluctuation dominate. Psychotic content is often fragmented or changeable.

Must-not-miss

Jealous/persecutory/erotomanic violence risk, stalking, treatment refusal.

High-risk causes5 causes

Jealous/persecutory/erotomanic violence risk
stalking
treatment refusal
violence
severe treatment refusal

Bedside question

Applies to the Delusions / Paranoia / Thought Interference / Command Phenomena group.

Often fixed, systematised, accompanied by hallucinations, thought disorder, or negative symptoms.

Helpful clues1 clue

Inattention and fluctuation dominate. Psychotic content is often fragmented or changeable.

Immediate action

Applies to the Delusions / Paranoia / Thought Interference / Command Phenomena group.

In older or medically unwell patients, assume delirium until proved otherwise Cannabis and stimulants can closely mimic primary psychosis Reassess once partially cleared Escalate early to medical/neurology review if red flags are present Consider MRI, EEG, CSF, and autoimmune testing when the syndrome is atypical Clarify positive symptoms, negative symptoms, cognition, and functional trajectory

Priority steps6 steps

1In older or medically unwell patients, assume delirium until proved otherwise
2Cannabis and stimulants can closely mimic primary psychosis
3Reassess once partially cleared
4Escalate early to medical/neurology review if red flags are present
5Consider MRI, EEG, CSF, and autoimmune testing when the syndrome is atypical
6Clarify positive symptoms, negative symptoms, cognition, and functional trajectory

Investigations

Applies to the Delusions / Paranoia / Thought Interference / Command Phenomena group.

Neuroimaging (CT/MRI), EEG, Lumbar puncture / CSF studies

Core tests3

Neuroimaging (CT/MRI)
EEG
Lumbar puncture / CSF studies

Mimics / overlap

Applies to the Delusions / Paranoia / Thought Interference / Command Phenomena group.

None listed

Consider

Points for this presentation

Applies to the Delusions / Paranoia / Thought Interference / Command Phenomena group — not specific to Delusional disorder

In older or medically unwell patients, assume delirium until proved otherwise
Cannabis and stimulants can closely mimic primary psychosis
Reassess once partially cleared
Escalate early to medical/neurology review if red flags are present

First-line tests

Applies to the Delusions / Paranoia / Thought Interference / Command Phenomena group — not specific to Delusional disorder

Neuroimaging (CT/MRI)
EEG
Lumbar puncture / CSF studies

Watch for

Jealous/persecutory/erotomanic violence risk
stalking
treatment refusal
Stalking
violence
severe treatment refusal

Also consider

Source and review

Review due· Unverified

v10 · exported 2026-07-11

Clinical reference — not validated decision support. Review before use.