Clinical Vignette
Patient: "Mrs. B" (62) and "Ms. B" (34, her daughter), referred jointly after neighbors contacted adult protective services. Both maintain that government agents are monitoring their home through hidden cameras.
Chief Concern: Mrs. B: "The government has been watching us for 3 years. They installed cameras in our smoke detectors and listening devices in the walls." Ms. B: "My mother is right. I've seen the evidence. We covered the smoke detectors with tape."
History of Present Illness: Mrs. B developed the belief 3 years ago that government agents installed surveillance equipment in her home. She covered smoke detectors, disconnected the doorbell, and taped over the laptop camera. She has no prior psychiatric history but became increasingly isolated after her husband's death 4 years ago. Ms. B moved in with her mother 2.5 years ago following a divorce. Initially skeptical of her mother's claims, Ms. B gradually adopted the beliefs over the following 6 months. She now reinforces and elaborates on the surveillance narrative. They have jointly disconnected internet service, stopped using cell phones, and covered all windows. They leave the home only for groceries. Ms. B previously worked as a dental hygienist and had an unremarkable social history. She has no independent psychiatric history and was described by her ex-husband as 'perfectly normal' during their marriage. Neighbors reported concern after noting covered windows and declining social contact.
Family History: Mrs. B: No known psychiatric history. Mr. B (deceased) had late-life depression. Ms. B: No psychiatric history prior to current symptoms.
Mental Status Exam: Mrs. B: Alert, cooperative, articulate. Speech organized, fluent. Affect constricted. Fixed persecutory delusion (government surveillance). Provides detailed, internally consistent account. No hallucinations. No disorganized thinking. Cognitive testing normal for age. Ms. B: Alert, deferential to mother during interview. When interviewed separately, repeats mother's beliefs with less detail and conviction. When asked 'Could you be wrong?', Ms. B states: 'I suppose it's possible, but my mother has shown me the evidence.' Mrs. B states: 'Absolutely not. The evidence is irrefutable.'
Step 1: Identifying the Primary and Secondary Cases
In shared psychotic presentations, a primary inducer develops delusions independently and a secondary individual adopts the beliefs through close contact. The distinction is critical for treatment planning:
Primary case (Mrs. B)
Delusion developed independently 3 years ago. Held with absolute conviction. Provides detailed, elaborated narrative. Denies any possibility of being wrong. Onset preceded daughter's involvement by 6 months. PRIMARY INDUCER IDENTIFIED.
Secondary case (Ms. B)
Initially skeptical. Gradually adopted beliefs after 6 months of close cohabitation. Less detailed and less certain when interviewed separately. Acknowledges possibility of being wrong ('I suppose it's possible'). No independent psychotic symptoms prior to cohabitation. SECONDARY (INDUCED) CASE IDENTIFIED.
Step 2: Diagnostic Classification
DSM-5-TR does not include 'Shared Psychotic Disorder' as a separate diagnosis (it was removed from DSM-5). The current approach requires diagnosing each individual independently:
| Individual | Assessment | DSM-5-TR Diagnosis | Rationale |
|---|---|---|---|
| Mrs. B (primary) | Fixed, non-bizarre persecutory delusion for 3 years. Preserved functioning outside delusional domain. No hallucinations, disorganized speech, or negative symptoms. | Delusional Disorder, Persecutory Type (F22) | Meets all criteria for DD. The delusion developed independently. |
| Ms. B (secondary) | Adopted shared delusional belief during close cohabitation. Lower conviction when separated. No independent psychotic symptoms. | Other Specified Schizophrenia Spectrum Disorder (F28) | Delusional symptoms occurring in the context of a close relationship with a delusional individual. Does not independently meet criteria for DD or Schizophrenia. |
Treatment Implications
Separation is diagnostic and therapeutic for the secondary case. When the secondary individual is removed from contact with the primary inducer, the shared delusions often attenuate or resolve — confirming the induced nature of the belief. Mrs. B (primary) requires treatment for Delusional Disorder (antipsychotic medication). Ms. B (secondary) may require only separation and supportive follow-up, with pharmacological treatment reserved for cases where beliefs persist after separation.
Diagnostic Formulation
Diagnostic Conclusion
Mrs. B: Delusional Disorder, Persecutory Type (F22): Primary inducer. Fixed persecutory delusion for 3 years with preserved global functioning. All DD criteria met. Independent treatment with antipsychotic medication indicated.
Ms. B: Other Specified Schizophrenia Spectrum Disorder (F28): Secondary (induced) case. Delusional symptoms adopted through sustained close contact with primary case. Lower conviction level. No independent psychotic pathology. Treatment plan: supervised separation from primary case with monitoring for belief resolution. Antipsychotic medication only if beliefs persist after separation.
Teaching Points
- Shared psychotic presentations (historically Folie à Deux) were classified as a separate diagnosis in DSM-IV (Shared Psychotic Disorder, 297.3). DSM-5-TR eliminated this category and requires independent diagnosis of each individual.
- The primary case develops delusions independently and typically has a more severe, treatment-resistant psychotic disorder (often Delusional Disorder or Schizophrenia). The secondary case is usually a dependent, socially isolated individual in close contact with the primary case.
- Risk factors for the secondary (induced) case include: social isolation (particularly dyadic isolation where the pair has limited outside contact), dependent personality traits, a submissive position in the relationship, intellectual disability, and cognitive vulnerability.
- Separation of the dyad is both diagnostic and therapeutic. Improvement in the secondary case's symptoms after separation confirms the induced nature. Persistence of symptoms suggests an independent psychotic disorder requiring its own treatment.
- Clinicians encountering shared delusional beliefs should always interview each individual separately. Joint interviews can mask differences in conviction level and allow the primary case to reinforce the secondary case's beliefs during the assessment.