Association of Schizoid and Schizotypal Personality disorder with violent crimes and homicides in Greek prisons.

Background: Personality disorders (PDs) have been associated with both violent crimes and homicides in many studies. The proportion of PDs among prisoners reaches up to 80%. For male prisoners, the most common PD in the literature is antisocial PD. The aim of this study was to investigate the association between PDs and violent crimes/homicides of male prisoners in Greece.

Methods: A sample of 308 subjects was randomly selected from a population of 1300 male prisoners incarcerated in two Greek prisons, one urban and one rural. The presence of PDs was assessed using the Mini International Neuropsychiatric Interview (MINI) and the Personality Diagnostic Questionnaire-4 (PDQ-4). Using logistic regression models PD types and PD "Clusters" (independent variables) were associated with "violent/non-violent crimes" and "homicides/non homicides" (dependent variables).

Results: "Cluster A" PDs (Paranoid, Schizoid, and Schizotypal) were diagnosed in 16.2%, "Cluster B" (Antisocial, Borderline, Histrionic, Narcissistic) in 66.9% and "Cluster C" (Obsessive-Compulsive, Dependent, Avoidant) in 2.9% of the studied population. Violent crimes and homicides were found significantly associated with "Cluster A" PDs ( = 0.022,  = 0.020). The odds ratio of committing violent crimes was 2.86 times higher for patients with "Cluster A" PDs than the ones without PDs. In addition, the odds ratio of committing homicides was 4.25 times higher for patients with "Cluster A" PDs. In separate analyses, the commitment of violent crimes as well as homicides, was significantly associated with Schizoid ( = 0.043,  = 0.020) and Schizotypal PD ( = 0.017,  = 0.030).

Conclusions: The majority of prisoners was found to suffer from a PD, mainly the Antisocial "Cluster B", but the commitment of violent crimes and homicides was significantly associated only with "Cluster A" PDs and specifically with Schizoid and Schizotypal PD.