Note: This is the IES-R not the 15 item version (IES).
Devised By:
The IES-R was developed by Daniel S. Weiss and Charles R. Marmar in
1997 to parallel the DSM-IV criteria for PTSD. The original IES was
developed prior to the adoption of Posttraumatic Stress Disorder as a
legitimate diagnosis in the DSM-III published in 1980, and only tap 2 of
the 4 criteria set out for PTSD in the DSM-IV: intrusion and avoidance
(Weiss & Marmar, 1997). IES-R was intended to tap hyperarousal cluster
of symptoms, the 4th criterion for PTSD.
Type of Instrument: The
IES-R is similar to IES in that it is a self-report measure designed to
assess current subjective distress for any specific life event. The IES-R
has 22 items, 7 items having being added to the original 15-item IES
(Weiss & Marmar, 1997). The 7 items comprise 6 that tap hyperarousal
symptoms such as: anger and irritability, heightened startle response,
difficulty concentrating, hypervigilance; and 1 new intrusion item that
taps the dissociative-like re-experiencing when experiencing true
flash-back. The hyperarousal subscale and the new intrusion item along
with the existing intrusion and avoidance subscales parallel the DSM-IV
criteria for PTSD.
The 7 items were randomly
interspersed with the existing 7 intrusion and 8 avoidance items. The only
modification to the IES items was the bifurcation of the item "I had
trouble falling asleep or staying asleep" into "I had trouble falling
asleep" (assigned to the hyperarousal subscale), and "I had trouble
staying asleep" (retained in the intrusion subscale).
Respondents are asked to
rate each item in the IES-R on a scale of 0 (not at all), 1 (a little
bit), 2 (moderately), 3 (quite a bit) and 4 (extremely) according to the
past 7 days.
Reliability:
In their study of 4
different population samples, Weiss and Marmar (1997) reported that the
internal consistency of the 3 subscales was found to be very high, with
intrusion alphas ranging from .87 to .92, avoidance alphas ranging from
.84 to .86, and hyperarousal alphas ranging from .79 to .90 (Briere,
1997).
Split-half/Cronbach's Alpha: NA
Test-Retest Reliability: Test-retest data were available for
2 of the samples in the Weiss and Marmar (1997) study. Data from sample 1
(n = 429) yielded the following test-retest correlation co-efficients for
the subscales: intrusion = .57, avoidance = .51, hyperarousal = .59. From sample 2 (n = 197) the
correlation coefficients were considerably higher: intrusion = .94,
avoidance = .89, hyperarousal = .92. It is believed that the shorter
interval between assessments and the greater recency of the traumatic
event for Sample 2 contributed to the higher coefficients of
stability.
Alternate Form Reliability: NA
Inter-rater Reliability:
NA
Validity:
Criterion (or Predictive) Validity:
Weiss and Marmar noted that the
hyperarousal subscale has good predictive validity with regard to trauma
(Briere, 1997). The intrusion and avoidance subscales, which are original
IES components, have been shown to detect change in repondents' clinical
status over time and detect relevant differences in the response to
traumatic events of varying severity (Weiss and Marmar, 1997, Horowitz et
al, 1979).
Content Validity: Not available for the hyperarousal subscale. The
intrusion and avoidance subscales which are originally IES items had high
endorsements of up to 85% (Horowitz, et al 1979).
Construct Validity: Weiss and Marmar (1997) utilised the
item-to-subscale correlation with that item removed from the subscale
generated by the standard alpha coefficient analyses. These were then
compared to the cross-subscale Pearson correlations. The results showed
that only 1 item ("I had trouble falling asleep") showed a stronger
relationship between it and a different subscale. The corrected
correlation of this item with its assigned hyperarousal subscale was .71,
and its correlation with the intrusion subscale was .79. Nineteen items
showed a correlation with their assigned subscale that was higher than
with the other subscales; and 2 items ("I had trouble staying asleep" and
" I avoided letting myself get upset when I though about it or was
reminded of it") showed a correlation that was equal.
The explanations given by
Weiss and Marmar (1997) for these results are that the 2 sleep items are
very highly correlated, driving a relationship between them in terms of
intrusion and hyperarousal; and as to the equal relationship of the
avoidance item with the avoidance and intrusion subscales, this may have
occurred because the presentation of the thought or the reminder invokes
intrusion, and the not dealing with it invokes avoidance.
Convergent Validity: NA
Discriminant Validity:
NA
Scoring Method:
Avoidance Subscale:
Mean of items 5, 7, 8 11, 12, 13, 17, 22
Intrusions Subscale:
Mean of items 1, 2, 3, 6, 9, 14, 16, 20
Hyperarousal
subscale:
Mean of items 4, 10, 15, 18, 19, 21
IES-R score:
Sum of the above 3 clinical scales.
For valid comparisons
with scores from the IES, use just the sum of the Avoidance and Intrusion
subscales.
Norms: NA
References:
Briere, J. (1997).
Psychological assessment of adult posttraumatic states. Washington
D.C.: American Psychological Association.
Horowitz, M., Wilner, M.,
and Alvarez, W. (1979). Impact of Event Scale: A measure of subjective
stress. Psychosomatic Medicine, 41, 209-218.
Weiss, D. & Marmar, C. (1997). The Impact of Event Scale -Revised. In J. Wilson & T. Keane (Eds), Assessing psychological trauma and PTSD. New York: Guildford.
Below is a list of difficulties people sometimes have after stressful life events. Please read each item, and then indicate how distressing each difficulty has been for you DURING THE PAST SEVEN DAYS with respect to __________________________________, how much were you distressed or bothered by these difficulties?
| Not at all | A little bit | Moderately | Quite a bit | Extremely | |
|
Any reminder brought back feelings about it |
0 |
1 |
2 |
3 |
4 |
|
I had trouble staying asleep |
0 |
1 |
2 |
3 |
4 |
|
Other things kept making me think about it |
0 |
1 |
2 |
3 |
4 |
|
I felt irritable and angry |
0 |
1 |
2 |
3 |
4 |
|
I avoided letting myself get upset when I thought about it or was reminded of it |
0 |
1 |
2 |
3 |
4 |
|
I thought about it when I didn’t mean to |
0 |
1 |
2 |
3 |
4 |
|
I felt as if it hadn’t happened or wasn’t real |
0 |
1 |
2 |
3 |
4 |
|
I stayed away from reminders about it |
0 |
1 |
2 |
3 |
4 |
|
Pictures about it popped into my mind |
0 |
1 |
2 |
3 |
4 |
|
I was jumpy and easily startled |
0 |
1 |
2 |
3 |
4 |
|
I tried not to think about it |
0 |
1 |
2 |
3 |
4 |
|
I was aware that I still had a lot of feelings about it, but I didn’t deal with them |
0 |
1 |
2 |
3 |
4 |
|
My feelings about it were kind of numb |
0 |
1 |
2 |
3 |
4 |
|
I found myself acting or feeling as though I was back at that time |
0 |
1 |
2 |
3 |
4 |
|
I had trouble falling asleep |
0 |
1 |
2 |
3 |
4 |
|
I had waves of strong feelings about it |
0 |
1 |
2 |
3 |
4 |
|
I tried to remove it from my memory |
0 |
1 |
2 |
3 |
4 |
|
I had trouble concentrating |
0 |
1 |
2 |
3 |
4 |
|
Reminders of it caused me to have physical reactions, such as sweating, trouble breathing, nausea, or a pounding heart |
0 |
1 |
2 |
3 |
4 |
|
I had dreams about it |
0 |
1 |
2 |
3 |
4 |
|
I felt watchful or on-guard
|
0 |
1 |
2 |
3 |
4 |
|
I tried not to talk about it |
0 |
1 |
2 |
3 |
4 |
Scoring:
Avoidance Subscale = mean of items 5, 7, 8, 11, 12,
13, 17, 22
Intrusion Subscale = mean of items 1, 2, 3, 6, 9, 14, 16,
20
Hyperarousal Subscale = mean of items 4, 10, 15, 18, 19, 21