Taking a History of Persistent Delusional Disorder

1. Establishing Rapport and Opening the Interview

• Begin with neutral, non-confrontational topics; patients with delusional disorder often preserve social functioning and appear entirely normal until the delusional topic arises.
• Do not challenge or agree with the delusion early in the interview - premature confrontation destroys rapport and may end the interview.
• Ask open questions: "Can you tell me what has brought you here today?" or "What has been worrying you recently?"

2. Presenting Complaint

• Clarify in the patient's own words what they believe is happening.
• Identify whether the presenting complaint is the delusion itself or a consequence of it (e.g., anxiety, legal trouble, social isolation, aggression).

3. History of the Delusion (Core of the Interview)

a) Content (Type)

b) Onset and Duration

• "When did you first notice these beliefs / experiences?"
• "Did they begin suddenly or gradually over weeks/months?"
• Determine whether symptoms have been present for >1 month (DSM-5-TR minimum) or >3 months (ICD-11 minimum).

c) Progression and Course

• Has the delusion stayed the same, expanded, or changed in content?
• Any periods of remission or partial improvement?
• Is the patient currently in a first episode, partial remission, or has there been a chronic continuous course?

d) Fixity and Intensity of Belief

• Ask about conviction on a 0-10 scale: "How certain are you that this is really happening?"
• Is the belief held with absolute certainty (true delusion) or are there moments of doubt (overvalued idea)?
• Has any evidence ever changed the patient's mind?

e) Systematization

• Is the delusion circumscribed/well-organized (typical of delusional disorder) or disorganized/bizarre?
• Does the patient construct an elaborate logical framework around the belief?

f) Preoccupation and Impact

• How much of the day is spent thinking about the delusion?
• Has it affected work, relationships, daily activities, or led to litigation or stalking behavior?

g) Precipitating Factors

• Any recent major stressors preceding onset: bereavement, job loss, retirement, financial hardship, social isolation, immigration, surgery, or debilitating illness?

4. Associated Psychotic Symptoms

• Hallucinations: In delusional disorder, hallucinations are absent or not prominent. If present, they must be related to the delusional content and transient.
  • "Do you ever hear voices or see things that others cannot?"
  • Prominent hallucinations should redirect your differential toward schizophrenia.
• Thought disorder: Speech should be coherent and logical; disorganized speech suggests schizophrenia.
• Negative symptoms: Social withdrawal, blunted affect, alogia - if prominent, reconsider schizophrenia.
• Bizarre content: "Is this something that could happen in real life, or is it more unusual?" - DSM-5 now allows "with bizarre content" as a specifier.

5. Mood History

• Screen thoroughly for depressive and manic episodes: "Have you felt very low, hopeless, or had thoughts of harming yourself? Have you had periods of abnormally elevated mood, needing little sleep, or feeling unusually powerful?"
• If mood episodes have occurred, establish their duration relative to the delusional periods.
• In delusional disorder, any mood episodes are brief relative to the duration of delusional periods - if they dominate, consider schizoaffective disorder or mood disorder with psychotic features.

6. Past Psychiatric History

• Previous episodes of psychosis, depression, mania, or anxiety disorders.
• Prior diagnosis of schizophrenia or schizoaffective disorder (which would exclude a diagnosis of delusional disorder).
• Previous psychiatric admissions, treatments, and response to antipsychotics.
• History of OCD or body dysmorphic disorder (which can present with delusional insight).

7. Medical and Neurological History

• Neurological: brain tumors, epilepsy, stroke, Alzheimer's disease, Lewy body dementia (psychotic features are common and early), Parkinson's disease with dementia, vascular dementia, frontotemporal dementia.
  • "Have you noticed any memory problems, confusion, or changes in thinking?"
• Metabolic and endocrine: thyroid disease, Cushing's syndrome, hepatic encephalopathy, vitamin B12/folate deficiency.
• Sensory impairments: hearing loss and visual impairment are risk factors for the development of delusional disorder in older adults.
• Infections: neurosyphilis, HIV encephalopathy.

8. Substance Use History

• Alcohol use disorder (delusional jealousy is classically associated).
• Stimulants (cocaine, amphetamines) can cause persistent paranoid psychosis.
• Cannabis, hallucinogens.
• Prescribed medications: corticosteroids, dopaminergic drugs (levodopa), mefloquine.

9. Family History

• Family history of schizophrenia (slightly elevated in delusional disorder, though strong association is unlikely per twin studies).
• Family history of mood disorders or delusional disorder.

10. Personal and Social History

• Developmental: premorbid personality (was the patient always suspicious, paranoid, or reclusive? - suggests paranoid personality disorder as a background).
• Social isolation: a key risk factor and consequence - "Do you have close friends or family you see regularly?"
• Marital history: especially for jealous type; any actual partner infidelity should be carefully explored.
• Occupational history: any decline or job loss related to the delusion?
• Immigration or cultural displacement: psychodynamic theory links persecutory delusions to the stresses of displacement.
• Forensic history: arrests, restraining orders, litigation (querulous/persecutory type), stalking (erotomanic type), violence toward alleged persecutors or partner (jealous type).

11. Insight and Judgment

• "Do you think there might be another explanation for what has been happening?"
• "Have others - family, friends, doctors - agreed with your concerns?"
• "Do you think you need any help or treatment?"
• In delusional disorder, insight is typically absent or poor regarding the delusion, though global functioning and judgment in non-delusional areas may be preserved.

12. Risk Assessment

• Homicidal risk: Particularly in persecutory type (directed at supposed persecutors) and jealous type (danger to partner).
  • "Have you ever felt like harming the person you believe has wronged you?"
• Suicidal risk: Depression can coexist; isolation and distress increase risk.
• Vulnerability: Is the patient being exploited due to their beliefs?
• Safeguarding: Partner in jealous-type delusion may be at serious risk of domestic violence or homicide.

Key Differentials to Exclude (Built into the History)

Summary of Key History Points

• Kaplan & Sadock's Comprehensive Textbook of Psychiatry (Diagnostic and Clinical Features, Delusional Disorder)
• Kaplan and Sadock's Synopsis of Psychiatry (Delusional Disorder in Geriatric Psychiatry)
• Kaplan & Sadock's Comprehensive Textbook - DSM-5-TR criteria and subtypes