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