The relationship between substance use disorders and aggression is complex and not only limited to direct effect of the drugs. Aggression increases the likelihood of substance abuse and is suggested to be a long term individual characteristic which is probably in association with personality traits preexisting before the substance use.

The aim of this study was to evaluate the relationship of personality dimensions with aggression among heroin dependent inpatients and to control the effect of psychiatric symptom severity on this relationship.

Participants were consecutively admitted male heroine (n=78) dependent inpatients. Patients were investigated with the Buss–Perry Aggression Questionnaire (BPAQ), the Temperament and Character Inventory (TCI) and the Symptom Checklist-Revised (SCL-90-R).

Character dimensions self-directedness (SD) and cooperativeness (C) were negatively and self-transcendence (ST) and severity of psychiatric symptoms were positively correlated with severity of aggression and its dimensions. Low SD and C, which are indicative of a personality disorder, were predictors of aggression. Other predictors for aggression in heroin dependents were higher persistence (P) and ST. Severity of psychiatric symptoms predicted aggression together with low C, and high P.

Aggression was more closely related with character dimensions rather than temperament dimensions. Nevertheless, low C and high P predicted the severity of aggression even when the severity of psychopathology was controlled. The careful evaluation of patients for the comorbid psychiatric disorders such as depression, anxiety and personality disorders are needed to handle aggression in heroin dependents which may be related with poor treatment outcome.