Validation of the Patient Health Questionnaire (PHQ–9) in an African context

Abstract

This research was aimed at validating the PHQ-9 in an African context. This study forms part of the project of Psychosocial Health and Biomarkers in an African context (FORT3, Wissing, 2008). The Patient Health Questionnaire (PHQ-9) is a nine-item depression scale that has the potential of being a dual-purpose instrument to establish the diagnosis of a depressive disorder, as well as the grade of symptom severity (Kroenke, Spitzer & Williams, 2001). The PHQ-9 was administered with criterion related measures to a multicultural convenience sample of 2214 participants from the North West Province of South Africa, including two groups of adolescents (n1 = 1480 and n2 = 559) and an availability sample of adults (n3 = 185). Instruments to determine criterion validity were the General Health Questionnaire (GHQ), designed to detect symptoms of mental disorders; the Mental Health Continuum - Short Form for Adults (MHC-SF) which measures the degree of emotional, social and psychological well-being; and the New General Self-Efficacy Scale (NGSE) designed to measure an individual's general self-efficacy. Descriptive statistics for the PHQ-9 including its reliability in the various groups is reported. The PHQ-9 manifested a Cronbach Alph are liability index of 0.86. Criterion-related validity was supported by significant correlations between the PHQ-9 and criterion measures. Confirmatory factor analysis for the PHQ-9 yielded a one-factor solution in all groups. The percentage variance explained ranged between 34.71% and 46.62%. Exploratory factor analyses yielded two factors in all groups with the second factor comprised of no more than 2 items and thus interpreted as a minor factor. The construct validity obtained in this research indicates that the PHQ-9 may be a valid measure to identify depression in a South African context. Based on the psychometric properties found in this study, it can be concluded that the PHQ-9 is a valid measure of depression in two of the samples selected for this study. Future studies may further validate this instrument in specific language and cultural groups, and explore the cross-cultural measurement equivalence.