Confirmatory factor analysis and factorial invariance analysis of the adolescent self-report Strengths and Difficulties Questionnaire: how important are method effects and minor factors?

OBJECTIVES. This study examined the factor structure of the self-report Strengths and Difficulties Questionnaire, paying special attention to the number of factors and to negative effects of reverse-worded items and minor factors within the subscales on model fit. Furthermore, factorial invariance across gender, age, level of education, and ethnicity was investigated. DESIGN. Data were obtained from the Youth Health Monitor Rotterdam, a community-based health surveillance system. METHODS. The sample consisted of 11,881 pupils of 11-16 years old. Next to the original five-factor model, a factor model with the number of factors based on parallel analysis and scree test was investigated. Confirmatory factor analysis for ordered-categorical measures was applied to examine the goodness-of-fit and factorial invariance of the factor models. RESULTS. After allowing reverse-worded items to cross-load on the prosocial behaviour factor and adding error correlations, a good fit to the data was found for the original five-factor model (emotional symptoms, conduct problems, hyperactivity-inattention, peer problems, prosocial behaviour) and a model with four factors (emotional symptoms and peer problems, conduct problems, hyperactivity-inattention, prosocial behaviour). Factorial invariance across gender, age, level of education, and ethnicity was found for the final five- and four-factor model, except for the prosocial factor of the four-factor model that showed partial invariance across gender. Conclusions. While support was found for both models, the final five-factor model is theoretically more plausible and gained additional support as the original scales emotional problems and peer problems showed different relations with gender, educational level, and ethnicity.