Evaluating the short form of the Reynolds Adolescent Depression Scale in New Zealand adolescents

Objective: The aim of the present study was to examine the reliability and validity of the short form of the Reynolds Adolescent Depression Scale (RADS-SF). Method: A sample of 9567 randomly selected New Zealand secondary school students participated in the Youth2000 Health and Wellbeing Survey that included the full-length version of the RADS. The reliability and validity of the subset of items that make up the RADS-SF and its comparability to the original version were assessed using Cronbach's alpha, kappa statistics, correlations between the two versions of the instrument, confirmatory factor analysis and correlation to other questions in the survey considered likely to be associated with depression. Results: The RADS-SF had Cronbach's alpha of 0.88, was strongly correlated (0.95) to the RADS, had acceptable fit for the data (chi(2) = 2823.27, df = 35, comparative fit index = 0.96, root mean square error of approximation = 0.092, 90% confidence interval = 0.089-0.095, standardized root mean square residual = 0.042), showed configural invariance across gender, age and ethnic groups, and was strongly correlated with other depression-related questions, such as suicidal ideation (r = 0.48). While the overall agreement for classification of depression by the two scores was good (kappa = 0.75), a higher percentage of students were classified as having depressive symptoms using the recommended RADS-SF cut-off point of 26 compared with the RADS criteria. Conclusions: The RADS-SF was found to have acceptable reliability and validity and to have psychometric properties comparable to the RADS in a large population of New Zealand adolescents.