Impact of Event Scale Revised IES-R
Impact of Event Scale Revised IES-R overview
Creator and Context
The Impact of Event Scale Revised (IES-R) is a 22 item self report measure of subjective distress following a specific stressful event.
It was developed by Daniel Weiss and Charles Marmar as a revision of the original 15 item Impact of Event Scale (Horowitz, Wilner and Alvarez, 1979), adding a hyperarousal subscale. The IES-R is copyrighted and is obtained from the author.
Presenting Conditions
The IES-R produces three subscale scores:
Intrusion (8 items): intrusive thoughts, images, dreams and waves of feeling
Avoidance (8 items): numbing, avoidance of feelings, situations and ideas
Hyperarousal (6 items): irritability, hypervigilance, difficulty concentrating and startle
Administration
Self administered. The person nominates a specific stressful event, then rates how distressing each difficulty has been over the past 7 days on a 5 point scale from 0 (not at all) to 4 (extremely).
Desired Audience
Adults who have experienced an identifiable traumatic or highly stressful event. Widely used in disaster response, road trauma, critical illness and community research.
The IES-R is best used to quantify event specific distress and to track how that distress changes over time. Its seven day recall window makes it responsive to short interval change, which suits regular review during acute post incident support.
Considerations
The IES-R is aligned to DSM-IV, not DSM-5. It does not fully assess negative alterations in cognition and mood, and the National Center for PTSD states that it is not used to diagnose PTSD.
Where DSM-5 aligned symptom monitoring is the goal, the PCL-5 is the better choice.
The frequently quoted total score threshold of 33 comes from a single veteran sample study and is not an author endorsed cut off.
The instrument is copyrighted and should be obtained from the author.
How to score the Impact of Event Scale Revised IES-R
Conducting the assessment
The person rates 22 items for the past 7 days on a 0 to 4 scale, in relation to one nominated event.
Interpretation
Total scores range from 0 to 88. The authors recommend using subscale means (0 to 4) rather than raw sums, so that scores can be compared with the SCL-90-R.
Creamer, Bell and Failla (2003) reported that a mean item score of 1.5, equivalent to a total of 33, gave the best diagnostic accuracy in a Vietnam veteran sample. This is a research derived threshold rather than an official cut off, and it should be treated with caution outside that population.
Clinical Considerations
Anchor the person to one specific event and keep it consistent across administrations, or the scores are not comparable.
Read the three subscales together. A high avoidance score with low intrusion often signals disengagement rather than recovery.
Do not use the IES-R to establish a PTSD diagnosis.
Impact of Event Scale Revised IES-R use cases
Measuring subjective distress after a specific event
Tracking change in intrusion, avoidance and hyperarousal over short intervals
Post incident and disaster response work
Research into event related distress
Category
Trauma
Research Summary
Weiss, D. S., & Marmar, C. R. (1996). The Impact of Event Scale Revised. In J. P. Wilson & T. M. Keane (Eds.), Assessing psychological trauma and PTSD (pp. 399 to 411). New York: Guilford Press.
Creamer, M., Bell, R., & Failla, S. (2003). Psychometric properties of the Impact of Event Scale Revised. Behaviour Research and Therapy, 41(12), 1489 to 1496.
Beck, J. G., Grant, D. M., Read, J. P., et al. (2008). The Impact of Event Scale Revised: Psychometric properties in a sample of motor vehicle accident survivors. Journal of Anxiety Disorders, 22(2), 187 to 198.
Other Assessment Guides
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Explore the Adverse Childhood Experience (ACE) Assessment, its development, significance, and application in psychological practice. Understand how to calculate ACE scores and interpret results.
PTSD Checklist for DSM-5 PCL-5
A practitioner guide to the PCL-5, the 20 item DSM-5 aligned measure of PTSD symptom severity. Covers administration, scoring, the 31 to 33 screening range and how to track treatment response.
Primary Care PTSD Screen for DSM-5 PC-PTSD-5
A guide to the PC-PTSD-5, the five item primary care screen for PTSD. Covers administration, the cut point of 4, sex differences in performance and when to escalate to a full assessment.
Note on Assessment licensing
Some assessments are copyright protected and require a licence or the copyright holder's permission for clinical, commercial or digital use. Where that applies, obtaining and maintaining that permission is the responsibility of the practice or organisation using the assessment. Tacklit provides the digital administration, scoring and reporting. We do not grant, transfer or supply rights to the underlying instrument.
