Dangerous delusions. Violence and the misidentification syndromes.

Among the mentally ill, those with well-developed delusions are more likely to commit violent crimes against persons than those with chronic, undifferentiated psychoses. Reports of violence associated with delusional misidentification are reviewed and four patients described who were either perpetrators or victims of assaults as a consequence of the syndromes of Frégoli, Intermetamorphosis, Subjective Doubles and Capgras. The cases illustrate the multiplicity of factors which have to be taken into consideration in order to predict whether an individual will act in a violent manner on these delusions.