How Much Distress Is Too Much on Deployed Operations? Validation of the Kessler Psychological Distress Scale (K10) for Application in Military Operational Settings

The aim of this study was threefold: (a) to assess the factor structure of the Kessler Psychological Distress Scale (K10) to determine whether interpreting the scale as a single dimensional measure of psychological distress is justified in military operational setting; (b) to validate the K10 for mental health surveillance in operational settings against self-reported occupational impairment; (c) to evaluate whether the K10 has better discriminatory power than de facto standards for mental health surveillance on deployment, namely the Patient Health Questionnaire and the Posttraumatic Stress Disorder Checklist, Civilian version. A convenience sample of Canadian Armed Forces personnel serving in Afghanistan (N = 1,264) completed self-report measures of psychological distress and occupational impairment. On examination of 6 competing models, the authors determined that interpreting the K10 as a measure of unspecified psychological distress is justified. Using receiver operating characteristic (ROC) curve analysis, they identified new cutoff values for dichotomous and polychotomous scoring methods. After comparing the area beneath the ROC curves for each of the 3 mental health surveillance questionnaires, the authors determined that all measures perform well as predictors of self-rated occupational impairment, with values ranging from .86 to .90. These results highlight the importance of cross-setting validation and demonstrate that validating psychological screening questionnaires against self-report measures of occupational impairment can be a useful strategy for understanding the manifestation of psychological distress on deployed military operations.