Cognitive neuropsychiatric analysis of an additional large Capgras delusion case series

Introduction: Although important to cognitive neuropsychiatry and theories of delusions, Capgras delusion has largely been reported in single case studies. Bell et al. (2017) previously deployed computational and clinical case identification on a large-scale medical records database to report a case series of 84 individuals with Capgras delusion. We replicated this approach on a new large-scale medical records database from an alternative provider of public mental health services in London while additionally examining associated instances of aggression, given previous claims that Capgras is a risk factor for violence.Methods: We identified 34 cases of Capgras delusion. Delusion phenomenology, clinical characteristics, and presence of lesions detected by neuroimaging were extracted.Results: Although most cases of Capgras involved misidentification of family members or partners, a notable minority (20.6%) included the misidentification of others. Capgras typically did not present as a monothematic delusion. Few cases had identifiable lesions with no evidence of a preponderance of right-hemisphere damage. There was no evidence of physical violence associated with Capgras delusion.Conclusions: The findings closely replicate Bell et al. (2017). The majority of Capgras delusion phenomenology is in line with the ‘dual route’ model although a significant minority of cases cannot be explained by this framework.