Testing competing models of the Strengths and Difficulties Questionnaire's (SDQ's) factor structure for the parent-informant instrument

The Strengths and Difficulties Questionnaire (SDQ) is a brief 25-item instrument that has been widely employed in clinical and epidemiological studies to assess children's psychological adjustment. Despite its widespread application in child and adolescent research, concerns have been expressed regarding the construct validity of the instrument and whether it might be tainted by a method factor that may undermine its utility as a diagnostic tool. We employed a confirmatory factor analytic approach to compare the goodness of fit of four competing models suggested by the extant literature for the parent-informant version of the questionnaire using data for 8514 nine-year-old children participating in the Growing Up in Ireland Study - a large population based cohort study in the Republic of Ireland. While analysis of the data provided support for the traditional five-factor conceptualisation of the instrument, a six-factor model which incorporated a method factor was found to fit the data marginally better. Nevertheless, we conclude that the existence of method effects does not present any great threat to the structural validity of the instrument taking account of patterns in the data and model parsimony. (C) 2012 Elsevier Ltd. All rights reserved.