Dimensional analysis of the Impact of Event Scale using structural equation modeling.

The dimensionality of the Impact of Event Scale (IES) was analyzed using structural equation modeling (SEM). Responses from 321 individuals (62% response) who had experienced a mass murder of seven people 8 months earlier were obtained. A model with a general factor and three subordinate specific factors--Intrusiveness, Avoidance, and Sleep Disturbance--was developed. Scores on the original IES subscales and the SEM factors were related to scores on the General Health Questionnaire. It was concluded that the original subscales could, to a certain degree, be regarded as a reflection of negative affectivity. A more differentiated pattern emerged using the specific latent variables from the SEM analysis.