Secondly, comorbidity of substance use in patients with schizophrenia is related to an increased risk of violent and even homicidal behavior and may even be a mediator in this relation . Thirdly, among persons with schizo-phrenia, dissocial personality and psychopathic traits have been shown to be related to both violent and non-violent crime. Moreover, some studies conclude that psychopathy is the best single
predictor of future violence in those with a mental illness. Despite the large amount of
literature concerning the role of positive symptoms, substance use, and psychopathic traits in the relation between schizophrenia and violence, it is not clear what the unique contribution is of each of these factors in different measures of aggression and violence.
Although aggression can be de fi ned in different ways and a
dichotomy might be somewhat simplistic, in the current paper we use reactive and proactive aggression as a distinction in aggression type Reactive aggression is a form of aggression as a reaction on a provocation and most of ten char-acterized by hostility. Information pro-cessing de fi cits are implicated in this type of aggression and may be associated with cognitive and perceptual features of the psy-chotic illness that lead to reactive aggression. Proactive (i.e. in-strumental or premeditated) aggression is a so called cold-blooded
form of aggression and of ten motivated by external reward. Therefore, besides its association with reactive ag-gression, psychopathy is also associated with proactive aggression.
The main aim of the present study was to examine the unique contribution of psychopathic traits, substance use, and persecutory ideations in the relation between these factors and different measures (and types) of aggression in inpatients with schizo-phrenia or related disorder. Based on the literature outlined above, we expected that psychopathic traits are associated to reactive aggressive behavior. Since substance use can be related to both reactive aggressionand to proactive aggression, no direct predictions are formulated for the relation between substance use and aggression.