This instrument, Impact of Event Scale (IES), evaluates the distress that is caused by traumatic events. The test is centered around two subscales – Intrusion, Avoidance, The IES-R is the revised edition of the original IES. IES 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 IES 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 IES. Their correlation rating, Horowitz and IES intrusion and avoidance, was 0.41.
Obtaining the IES
Via his website the scale’s author, Mardi Horowitz, M.D., grants permission to download and use the IES for non-profit research or clinical work. See http://www.mardihorowitz.com/permissions
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.
