Shared psychotic disorder: a critical review of the literature

To search the literature to reassess the concept of shared psychotic disorder (SPD) using modern nosology and current biopsychosocial formulation.

Analyzing published case reports from 1942 through to 1993 that meet DSM-IV criteria for SPD according to patient age, sex, nature and duration of the relationship with the "primary", length of exposure to primary's psychosis, family psychiatric history, comorbidity, social isolation of the dyad, presence of hallucinations, delusional type, and the diagnosis of the primary.

Findings revealed: 1. males and females were affected with equal frequency; 2. there was equal prevalence in younger and older patients; 3. the majority of shared psychoses (90.2%) were equally distributed among married couples, siblings, and parent-child dyads; 4. comorbid dementia, depression, and mental retardation were common; 5. hallucinations were common; 6. the majority of dyads (67.3%) were socially isolated.

SPD probably occurs in premorbidly disposed individuals in the context of social isolation which is shared with a psychotic person.