Measuring the Emotional Impact of an Event

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How to Use an Effective PTSD Test

By Steve B. Reed, LPC, LMSW, LMFT © 2007

What is the Impact of Event Scale?

The Impact of Event Scale (IES) is a short set of 15 questions that can measure the amount of distress that you associate with a specific event.  Developed in 1979 by Mardi Horowitz, Nancy Wilner, and William Alvarez, it continues to find use in research and with mental health professionals worldwide.

The test is often useful in measuring the impact that you experience following a traumatic event.  Studies show the IES valuable in spotting both trauma and less intense forms of stress. It will show how much an impact event is currently bothering you.  The IES is even capable of detecting the effect of the most severe impact events, those that can leave you suffering from Post Traumatic Stress Disorder (PTSD).

In 1997, Daniel S. Weiss and Charles R. Marmar chose to revise the scale by adding seven additional questions to measure another dimension of people's reactions to intense stress events.  Both versions have been found to be valid and reliable.1, 2

I frequently utilize this tool to measure distress before providing treatment with EMDR or the REMAP process and then again, a week or two after treatment to help measure how much EMDR or REMAP has helped.

Here are the questions and instructions for the original Impact of Event Scale.

List Today's Date_________

List the Date of the Event_________

Describe the Event______________________________________________

Below is a list of comments made by people after stressful life events.  Please mark each item, indicating how frequently these comments were true for you during the past seven days.  If they did not occur during that time, please mark the "not at all" column.

Select only one answer per row.

Not at allRarelySometimesOften
1.I thought about it when I didn't mean to.      0      1        3    5
2.I avoided letting myself get upset when I thought about it or was reminded about it.      0      1        3    5
3.I tried to remove it from my memory.      0      1        3    5
4.I had trouble falling asleep or staying asleep because of pictures or thoughts about it that came to my mind.      0      1        3    5
5.I had waves of strong feelings about it.      0      1        3    5
6.I had dreams about it.      0      1        3    5
7.I stayed away from reminders about it.      0      1        3    5
8.I felt as if it hadn't happened or was unreal.      0      1        3    5
9.I tried not to talk about it.      0      1        3    5
10.Pictures about it popped into my mind.      0      1        3    5
11.Other things kept making me think about it.      0      1        3    5
12.I was aware that I still had a lot of feelings about it, but I didn't deal with them.      0      1        3    5
13.I tried not to think about it.      0      1        3    5
14.Any reminder brought back feelings about it.      0      1        3    5
15.My feelings about it were kind of numb.      0      1        3    5
      0 +___   +______  +__ =___

Scoring: Total each column and add them together for a total stress score.

For example, every item marked in the "not at all" column is valued at 0.  In the "rarely" column, each item is valued at a 1.  In the "sometimes" column every item marked has a value of 3 and in the "often" column each item is valued at 5.  Add the totals from each of the columns to get the total stress score.

The next section will help you to understand the significance of your score.

What Does My Score on the Impact of Event Scale Mean? 

The Impact of Event Scale1 (Horowitz, 1979) and the Impact of Event Scale-Revised2 (Weiss, 1997) are useful in measuring how a stressful event may affect you.  For example on the original 15-item Impact of Event Scale (IES), the scores can range from 0 to 75.  You can interpret the IES scores in the following way:3

Original Impact of Event Scale (15 questions):

0 –   8        No Meaningful Impact

9 – 25        Impact Event—You may be affected.

26 – 43        Powerful Impact Event—You are certainly affected.

44 – 75        Severe Impact Event—This is capable of altering your ability to function.

Scores above 26 are very important.  Here are some examples of what is associated with scores this high.

Score (IES)      Consequence

27or moreThere is a 75% chance that you have Post Traumatic Stress Disorder
(PTSD).4   Those who do not have full PTSD may have partial PTSD or at least some of the symptoms.
35and aboveThis represents the best cutoff for a probable diagnosis of PTSD.5   Consider consulting a mental health professional who is skilled in treating such issues.

Impact of Event Scale (22 questions):

The revised version of the Impact of Event Scale (IES-r) has seven additional questions and a scoring range of 0 to 88.

On this test, scores that exceed 24 can be quite meaningful.  High scores have the following associations.

Score (IES-r)    Consequence

24or morePTSD is a clinical concern.6   Those with scores this high who do not have full PTSD will have partial PTSD or at least some of the symptoms.
33and aboveThis represents the best cutoff for a probable diagnosis of PTSD.7
37or moreThis is high enough to suppress your immune system's functioning (even 10 years after an impact event).On the original IES, a comparable score would be approximately 39.

I work with both the original and revised versions of the Impact of Event Scale.  I find these tests very helpful in measuring the effect of routine life stress, everyday traumas, and acute stress.

When to Use the Impact of Event Scale?

I have found it clinically beneficial to use this instrument with a variety of issues. Especially any presenting problem that is likely to affect the emotional midbrain. This can include three key areas:

  1. Traumatic Events (war trauma, being robbed at gunpoint, domestic violence, child abuse, injury auto accidents, seeing someone killed, etc.)
  2. Panic Attacks
  3. Phobias (fear of driving on highways, panic attacks while driving, fear of bridges, fear of flying, airplane turbulence fear, needle phobias, elevator phobia, fear of heights, etc.)

In addition to the above-mentioned uses, I have also found this instrument helpful as a measurement tool in anxiety treatment.

The Impact of Event Scale provides a helpful tool for assessing the effect of high-stress events. I have found it a valuable way to measure therapeutic progress from pre-treatment to post-treatment.


  1. Horowitz, M. Wilner, N. & Alvarez, W. (1979). Impact of Event Scale: A measure of subjective stress. Psychosomatic Medicine, 41, 209-218.
  2. Weiss, D.S., & Marmar, C.R. (1997). The Impact of Event Scale-Revised. In J.P. Wilson & T.M. Keane (Eds.), Assessing Psychological Trauma and PTSD (pp.399-411). New York: Guilford.
  3. Hutchins, E. & Devilly, G.J. (2005). Impact of Events Scale. Victim's Web Site.
  4. Coffey, S.F. & Berglind, G. (2006). Screening for PTSD in motor vehicle accident survivors using PSS-SR and IES. Journal of Traumatic Stress. 19 (1): 119-128.
  5. Neal, L.A., Walter, B., Rollins, J., et al. (1994). Convergent Validity of Measures of Post-Traumatic Stress Disorder in a Mixed Military and Civilian Population. Journal of Traumatic Stress. 7 (3): 447-455.
  6. Asukai, N. Kato, H. et al. (2002). Reliability and validity of the Japanese-language version of the Impact of event scale-revised (IES-R-J). Journal of Nervous and Mental Disease. 190 (3): 175-182.
  7. Creamer, M. Bell, R. & Falilla, S. (2002). Psychometric properties of the Impact of Event Scale-Revised. Behaviour Research and Therapy. 41: 1489-1496.
  8. Kawamura, N. Yoshiharu, K. & Nozomu, A. (2001) Suppression of Cellular Immunity in Men with a Past History of Post Traumatic Stress Disorder. American Journal of Psychiatry. 158: 484-486

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