Screening for serious mental illness in the general population with the K6 screening scale: results from the WHO World Mental Health (WMH) survey initiative

Abstract

Data are reported on the background and performance of the K6 screening scale for serious mental illness (SMI) in the World Health Organization (WHO) World Mental Health (WMH) surveys. The K6 is a 6-item scale developed to provide a brief valid screen for DSM-IV SMI based on the criteria in the US ADAMHA Reorganization Act. Although methodological studies have documented good K6 validity in a number of countries, optimal scoring rules have never been proposed. Such rules are presented here based on analysis of K6 data in nationally or regionally representative WMH surveys in 14 countries (combined n = 41,770 respondents). Twelve-month prevalence of DSM-IV SMI was assessed with the fully-structured WHO Composite International Diagnostic Interview. Nested logistic regression analysis was used to generate estimates of the predicted probability of SMI for each respondent from K6 scores taking into consideration the possibility of variable concordance as a function of respondent age, gender, education, and country. Concordance, assessed by calculating the area under the receiver operating characteristic curve (AUC), was generally substantial (Median .83; Range .76-.89; Inter-quartile range .81-.85). Based on this result, optimal scaling rules are presented for use by investigators working with the K6 scale in the countries studied.

Health consequences of the US Deferred Action for Childhood Arrivals (DACA) immigration programme: a quasi-experimental study

“…30,31 The K6 was administered only to a randomly selected one-third sample of NHIS respondents. The K6 has been shown to have high reliability, validity, and internal consistency in identifying of the symptoms serious mental illness as denoted by the DSM-IV.…”

“…The K6 has been shown to have high reliability, validity, and internal consistency in identifying of the symptoms serious mental illness as denoted by the DSM-IV. 30 We also used these variables to specify binary outcomes denoting self-reported classifications of poor or fair health (vs good, very good, or excellent health) and presence of moderate or worse psychological distress (K6 score ≥5). 31 …”

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“…The K6 was originally developed as a unidimensional measure of non-specific psychological distress for the U.S. National Health Interview Survey (NHIS) and has since been implemented in the U.S. National Household Survey on Drug Abuse (NHSDA), the Australian National Survey of Mental Health and Well-Being, and many community-based studies of mental health. Repeated psychometric testing of the K6 in nationally representative and community-based samples indicates that the scale has strong reliability and validity (Kessler et al 2002(Kessler et al , 2003(Kessler et al , 2010Mewton et al 2016). Importantly, the K6 demonstrates strong discrimination properties that correlate scale scores with clinically significant indicators of probable severe mental illness (Kessler et al 2010).…”

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“…K6 dichotomous score groupings were then applied in the data analysis, with the sum scores between 6-18 and 19-30 being classified as 'no probable serious mental illness' and 'probable serious mental illness' respectively. [21][22][23] Respondents' reported highest completed level of education was recoded to distinguish between those who had not (yet) completed secondary school, those who had completed secondary school and those who had completed post-secondary education. To approximate the gross annual household income quintiles reported by the Australian Bureau of Statistics for 2009-10, 24 respondents' reported annual income was grouped into five categories: very low (less than $28 000), low ($28 001-$52 000), middle ($52 001-$83 000), high ($83 001-$125 000) and very high (more than $125 000).…”