Frequency and severity approaches to indexing exposure to trauma: the Critical Incident History Questionnaire for police officers.

The Critical Incident History Questionnaire indexes cumulative exposure to traumatic incidents in police by examining incident frequency and rated severity. In over 700 officers, event severity was negatively correlated (r(s) = -.61) with frequency of exposure. Cumulative exposure indices that varied emphasis on frequency and severity-using both nomothetic and idiographic methods-all showed satisfactory psychometric properties and similar correlates. All indices were only modestly related to posttraumatic stress disorder (PTSD) symptoms. Ratings of incident severity were not influenced by whether officers had ever experienced the incident. Because no index summarizing cumulative exposure to trauma had superior validity, our findings suggest that precision is not increased if frequency is weighted by severity.