The performance of the K6 scale in a large school sample: A follow-up study evaluating measurement invariance on the Idaho Youth Prevention Survey.

Since 2013, Idaho has been building capacity and infrastructure through the Strategic Prevention Framework State Incentive Grant to prevent substance abuse and related problems, namely psychiatric morbidity. As this federal initiative requires states to engage in data-driven strategic planning at the state and community levels, clinically validated instruments are particularly valuable in the context of school surveys that have limited space and require timely administration. Thus, the K6 scale was included on the 2014 Idaho Youth Prevention Survey as a measure of nonspecific psychological distress. To verify the unidimensional structure of the K6, principal axis and confirmatory factor analyses were performed in a school-based sample of Idaho students (n = 12,150). A series of multigroup confirmatory factor analyses were then performed to evaluate measurement invariance across gender, age, and race. Overall, the prevalence of serious psychological distress in the past 30 days was 17.2% in Idaho. Factor analyses confirmed the 1-factor solution of the K6. Four levels of measurement invariance were demonstrated across gender, age, and race. Together, these results further illustrate the construct validity of the K6 for use in adolescent populations. Other states are encouraged to include the K6 on their school surveys to facilitate policy planning and resource allocation as well as generate cross-state comparisons. (PsycINFO Database Record (c) 2016 APA, all rights reserved).