Construct validity of the five-factor Strengths and Difficulties Questionnaire (SDQ) in pre-, early, and late adolescence

The Strengths and Difficulties Questionnaire (SDQ) is designed to measure psychological adjustment in children and adolescents. Psychometric evaluations of the instrument have shown satisfactory convergent and discriminant validity, while factor analysis studies have shown mixed results across countries. In the present study, the construct validity of the five-factor SDQ is evaluated in a large community sample of Norwegian pre-, early, and late adolescents. The sample consisted of 26,269 children and adolescents (10-19 years) with valid answers on all 25 items of the SDQ self-report. Complete parent/proxy data of respective pre-adolescent children was available for 6,645 cases. A Lisrel approach to Confirmatory Factor Analysis (CFA) was used to evaluate the five-factor model and the presence of a positive construal factor. In the sample of pre-adolescents and their parents/proxies, convergent and discriminant validity was evaluated by a CFA approach to multitrait-multimethods (MTMM). Fit statistics for the hypothesized five-factor model were satisfactory, but introducing correlated error terms for some of the items led to significant model improvement in all age groups. All factor loadings were higher than .30, except for item 11 (good friend). The loadings differed across age groups and differed markedly between the parent/proxy and self-report measures. The MTMM showed that the source of ratings made a difference on the validity of all subscale ratings, with self-reports discriminating more on ratings of emotional and peer problems, and parents/proxies discriminating more on hyperactivity symptoms. A positive construal factor was identified but had a modest effect compared with the original five traits. Results suggested an unclear construct and meaning of the Prosocial behaviour subscale. The results of the present study indicated support for the proposed five-factor structure of the SDQ (Goodman, 2001) across a wide age range (10-19years), including older adolescents and different informants. However, some improvements should be considered to improve internal reliability and conceptual clarity.