Reliability of the Impulsive–Premeditated Aggression Scale (IPAS) in treated opiate-dependent individuals

The purpose of the study was to evaluate the internal consistency and test–retest reliability of the Impulsive Aggression (IA) and Premeditated Aggression (PM) scales of the Impulsive–Premeditated Aggression Scale (IPAS) in male and female substance-dependent patients, and to compare the findings to those obtained on widely used, validated measures of aggression. Using a sample of 121 patients (61 women) in methadone maintenance treatment, 69 (35 women) of which were re-evaluated after a minimum of 2 weeks, the IPAS scales showed acceptable internal consistency (α > .72) and test–retest reliability (ICC > .54). These results were comparable to the other aggression measures, and results among women were comparable to men. This was the first study to examine the IPAS scales in a substance use population, to contain a sufficient sample of women for sub-analyses, and to examine the stability of the measure. Findings support the internal consistency and test–retest reliability of the IPAS in male and female opiate-dependent individuals.