This instrument, Impact of Event Scale (IES), evaluates the distress that is caused by traumatic events. The test is centered around two subscales – Intrusion and Avoidance. The IES-R is the revised edition of the original. The instrument is closely connected with symptoms of PTSD.
The format for the test is a 22-item self-report in which respondents identify an stressful event and then respond to question measuring distress with a 5-point scale.
Authors: Horowitz, Wilner, & Alvarez (1979).
Validity and Reliability
The Impact of Event Scale has a reported Cronbach alpha rating of .79-.91 (Intrusion) and .82-.90 (Avoidance) dependent on studies from Zilberg (1982), Weiss & Marmar (1997), Classen (1998), and Briere & Elliott (1998). Presented by Solomon & Mikulincer (1988), the test-retest reliability for the Impact of Event Scale was estimated at 0.56 – .74, based on a two different samples. Horowitz’ theory on stress response syndrome reveals two common response to stress with the scale. Their correlation rating, Horowitz and IES intrusion and avoidance, was 0.41.
Obtaining the IES
Mardi Horowitz grants permission via his website to download and use the IES for non-profit research or clinical work.
References
Hendrix, C. C., Jurich, A. P., & Schumm, W. R. (1994). Validation of the Impact of Event Scale on a sample of American Vietnam veterans. Psychological Reports, 75, 321-322.
Horowitz, M. J., Wilner, N. R., & Alvarez, W. (1979). Impact of Event Scale. A measure of subjective stress. Psychosomatic Medicine, 41, 209-218.
Orsillo, S. M. (2001). Measures for acute stress disorder and posttraumatic stress disorder. In M.M. Antony & S. M. Orsillo (Eds.), Practitioner’s guide to empirically based measures of anxiety (pp. 255-307). New York: KluwerAcademic/Plenum.
Weiss, D. S., & Marmar, C. R. (1996). The Impact of Event Scale – Revised. In J. Wilson & T. M. Keane (Eds.), Assessing psychological trauma and PTSD (pp. 399-411). New York: Guilford.
