Brief measure of posttraumatic stress reactions: Impact of Event Scale-6

The Impact of Event Scale-revised (IES-R) is one of the most widely used measures of posttraumatic stress reactions. However, for some purposes, such as large epidemiological studies, there is a need for briefer instruments. The aim of this study was to develop and validate an abbreviated version of the IES-R that could capture the three current symptom clusters of posttraumatic stress disorder (PTSD). Stepwise multiple regression was applied to abbreviate the IES-R in one sample. The abbreviated version was then tested in three separate samples of individuals exposed to different kinds of potentially traumatic events. Agreement with a reference measure of PTSD, the PTSD checklist (PCL), was calculated for the abbreviated and the full-scale versions of IES. The abbreviation procedure resulted in a subset of six items (the IES-6), which correlated highly (pooled correlation = 0.95) with the IES-R across samples. Correlations between the IES-6 and IES-R subscales were somewhat lower (r = 0.78-0.94). Both the IES-6 and IES-R were in high agreement with the PCL. The IES-6 appears to be a robust brief measure of posttraumatic stress reactions. It may be useful for research in epidemiological studies, and it may also have a role as a screening instrument in clinical practice.