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Factor analytic structure of the Impact of Events Scale – Revised when used with a firefighting sample

Shannon L. Wagner (Health Science Program, University of Northern British Columbia, Prince George, Canada)

Disaster Prevention and Management

ISSN: 0965-3562

Article publication date: 8 November 2011



The Impact of Events Scale (IES)/Impact of Events Scale – Revised (IES‐R) is arguably one of the most well known tools used to assess post‐traumatic symptomatology. The background literature reveals a significant gap with respect to the structural properties of the IES/IES‐R when used with emergency service populations. In response to these identified gaps, this paper aims to provide an evaluation of the structural properties of the three‐factor IES‐R when used specifically with a firefighting sample.


Responses to IES‐R for a sample of paid‐professional firefighters (n=94) and a sample of similar comparison participants (n=91) were evaluated for support of the suggested IES‐R subscales – i.e. hyperarousal, avoidance and intrusions. Responses for both groups were entered into a three‐factor maximum likelihood factor analysis with direct oblimin rotation.


The results provide further support for the use of these subscales when the IES‐R is employed with a community sample. However, the factor structure for the three suggested subscales was not supported for the firefighters' responses. With the firefighting sample, some items for the intrusion subscale loaded as expected, but no discernible pattern was evident for the hyperarousal or avoidance subscales. Given the lack of support for a three‐factor structure with the firefighting sample, scree plot analysis was used to suggest that a two‐factor solution may provide the best fit solution. The two‐factor solution revealed a construct described as general “post‐traumatic symptomatology” and a potential second factor described as “sleep”.


The author suggests a conservative approach to using the IES‐R with first responder samples, in particular firefighters, and recommends the use of an overall score in place of subscale scores. This recommendation is suggested as a temporary approach until additional research can be completed to further evaluate the present lack of support for the three IES‐R subscales when used with a firefighting sample.



Wagner, S.L. (2011), "Factor analytic structure of the Impact of Events Scale – Revised when used with a firefighting sample", Disaster Prevention and Management, Vol. 20 No. 5, pp. 473-484.



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