A 40-year-old woman and her 16-year-old daughter, who live in isolation after migrating, share an identical delusional belief that their landlord controls their thoughts through the water supply. When separated for two weeks during admission, the mother retains the delusion while the daughter's belief gradually fades. What is the diagnosis in the daughter?

• A Paranoid schizophrenia
• B Induced delusional disorder (folie a deux) ✓
• C Delusional disorder, persecutory type
• D Brief psychotic disorder with marked stressor

Explanation

Induced delusional disorder, traditionally called folie a deux, occurs when a delusion held by a dominant partner is adopted by a closely associated, usually submissive and socially isolated person. The diagnostic hallmark demonstrated here is resolution or marked reduction of the delusion after separation from the primary case. Schizophrenia and primary delusional disorder persist independently of separation, and the daughter's content is identical to the inducer rather than arising from her own stress response.

Reference: ICD-11 Classification of Mental and Behavioural Disorders, 2022 ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.