Homicides committed by delusional patients in the early 20th and 21st centuries: A study conducted in a French secure unit.

Homicides committed by delusional patients are the object of a rich scientific literature, which puts the risk of such acts occurring into perspective when analyzing the offenders' sociodemographic and clinical characteristics. However, few articles detail the themes and mechanisms underlying those patients' delusions. To help bridge that gap, the authors conducted this retrospective descriptive study, including two samples of delusional homicidal patients, one from near present day and one from nearly a century ago. This study considered similarities observed in the literature (such as patients' sociodemographic profile, clinical data, and acting-out dynamics), but also explored the characteristics of delusion. In the 2015-2019 sample, the typical patient profile was: single male (31.5 years old on average), without child, unemployed, and with psychiatric history (56.6%). Most patients suffered from schizophrenic disease (83%) with non-systematized delusions exhibiting multiple themes in 80% of cases. Four principal types of delusion were observed: persecutive (100%), mystical (43.3%), megalomaniac (30%), and bodily (30%). The mechanisms were interpretative, hallucinatory, and intuitive. There was a societal influence in 23.3% of the cases (most often terrorist acts). The 1910-1914 historical sample revealed several differences: patients were older, more often married and employed. There were more diagnoses of chronic delusional disorder (30%). Persecutory delusion was constant (100%), and the other delusional themes were the "intimate relationship" type (50%)-jealousy, erotomanic-and the bodily type (40%). Additional studies are useful in order to reinforce our findings, and to further investigate the possibilities of prevention.