Development of the Observation Scale for Aggressive Behavior (OSAB) for Dutch forensic psychiatric inpatients with an antisocial personality disorder

The Observation Scale for Aggressive Behavior (OSAB) has been developed to evaluate inpatient treatment programs designed to reduce aggressive behavior in Dutch forensic psychiatric patients with an antisocial personality disorder, who are “placed at the disposal of the government”. The scale should have the sensitivity to measure changes in the possible determinants of aggressive behavior, such as limited control of displayed negative emotions (irritation, anger or rage) and a general deficiency of social skills. In developing the OSAB 40 items were selected from a pool of 82 and distributed among the following a priori scales: Irritation/anger, Anxiety/gloominess, Aggressive behavior, Antecedent (to aggressive behavior), Sanction (for aggressive behavior) and Social behavior. The internal consistency of these subscales was good, the inter-rater reliability was moderate to good, and the test–retest reliability over a two to three week period was moderate to good. The correlation between the subscales Irritation/anger, Anxiety/gloominess, Aggressive behavior, Antecedent, Sanction was substantial and significant, but the anticipated negative correlation between these subscales and the Social behavior subscale could not be shown. Relationships between the corresponding subscales of the OSAB and the FIOS, used to calculate concurrent validity, yielded relatively high correlations. The validity of the various OSAB subscales could be further supported by significant correlations with the PCL-R and by significant but weak correlations with corresponding subscales of the self-report questionnaires. The Observation Scale for Aggressive Behavior (OSAB) seems to measure aggressive behavior in Dutch forensic psychiatric inpatients with an antisocial personality disorder reliably and validly. Contrary to expectations, a negative relationship was not found between aggressive and social behavior in either the OSAB or FIOS, which were used for calculating concurrent validity.