The featured paper is ‘Horowitz’s Impact of Event Scale Evaluation of 20 Years of Use’ by Sundin and Horowitz published in 2003 and which is freely available here.
The authors introduce the scale by suggesting it’s widespread use may be due to 2 features
1. Ease of use in picking up severe PTSD
2. Theoretical basis in information processing theories about adapting to significant life events
There were a number of aims stated by the authors – they wanted to examine the relationship of the scores on the IES to a number of different factors
1. Type of event
2. Time elapsed since trauma
5. Country where study performed
6. Year of publication
The author’s method was complex and involved multiple combinations of approaches. The authors aggregated studies with small sample sizes (by utilising the average IES scores and standard deviations), performed a separate analysis of studies using a modified IES (e.g. where participants weren’t able to sleep between the event and the study, a question about sleep was removed), hierarchical multiple regression analysis for the effects of different factors on IES scores supported by use of scatter plots for bivariate relations between factors of interest and finally creation of dummy variables to explore the relationship between scores and country in which study was performed. Non-english papers were excluded.
The authors reported a number of findings
1. A weak correlation between age and higher scores on the intrusive subscale
2. IES subscale scores tended to increase from (Norway, Germany and the Netherlands) to United States to (England, Australia and Israel)
3. Comparison groups (i.e. control group) had lowest scores on the IES whereas war victims had the highest scores
4. The relationship between IES scores and type of event was modified by time from event
5. Intrusive subscale scores decreased over time
In the discussion the authors begin by making a very interesting point – that they had omitted the hyperarousal experiences because they didn’t factor together although these have been included in the PTSD criteria in DSM-IV although adding that the IES is not intended to be used for establishing a diagnosis. The authors commented on the significant findings with regards to type of events and time from trauma and also comment on the difficulties of assessing the scores in the comparison groups who did not have a significant event to refer to when completing the IES. The authors add that there were a number of other variables not considered which contributed to the variance thus throwing down the gauntlet for future researchers!
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