Folie a plusieurs: forensic cases from nineteenth-century Ireland

Folie a plusieurs is a syndrome in which two or more individuals share symptoms (e.g., delusions). This paper uses archival material to present and discuss forensic psychiatric cases of folie a plusieurs from nineteenth-century Ireland. The cases of three brothers who all 'became insane at the same time' and killed another brother illustrate: the role of organic factors in folie a plusieurs; the use of 'moral management' strategies; and the problem of tuberculosis in asylums. The case of one woman whose family 'all became insane at once' and killed one of her sons illustrates: the importance of identifying the 'primary' patient; the difficulties experienced by 'secondary' cases; and the limited therapeutic progress achieved in nineteenth-century asylums. While further historical study is required to explain the emergence of the concept of folie a plusieurs in the late nineteenth century, it is clear that, over one hundred years since the term came to prominence, 'communicated insanity' still presents substantive diagnostic, clinical and ethical challenges to mental health and judicial services.