Development and validation of a 6-day standard for the identification of frequent mental distress

The goals of the current study were to assess the concurrent validity of a single-item measure of general mental distress with established, multi-item mental health measures used in population-level surveillance and to establish the optimal cutpoint for determining psychological distress (previously identified as frequent mental distress) using recently available data from the Behavioral Risk Factor Surveillance System survey. Data for this study were obtained from the core questionnaire and two optional modules available as part of the 2006 and 2007 Behavioral Risk Factor Surveillance System (BRFSS) surveys. Frequent mental distress (FMD) was identified by the number of days of self-reported poor mental health during the last 30 days. Comparisons of the number of days with poor mental health and positive scores for measures of depression and serious mental illness were calculated to identify the most efficient cutpoint for establishing FMD. Comparisons of results obtained from ROC analyses using the PHQ-8 and K6 reported 0.867 (95% CI 0.861-0.872) and 0.840 (95% CI 0.836-0.845) of the area under the curve, respectively, suggesting good accuracy. Using the Youden index, 6 days of poor mental health in the past 30 days, rather than the existing 14-day standard, was identified as the point at which the sum of the sensitivity and specificity was greatest. Results from this study suggest that a 6-day standard (FMD-6) can be used as a valid and reliable indicator of generalized mental distress with strong associations to both diagnosable depressive symptomology and serious mental illness.