Measurement invariance of the Strengths and Difficulties Questionnaire (SDQ) across age groups in a German...

The Strengths and Difficulties Questionnaire (SDQ) is widely used to assess child and adolescent mental health. Ensuring measurement invariance (MI) across developmental stages is critical for valid comparisons. Previous studies have assessed MI across various demographic subgroups, but research on MI across age groups remains limited, particularly using rigorous methodological approaches. Using data from the representative German Motorik-Modul Study, we tested MI of the German version of the SDQ across four age groups (3-5, 6-10, 11-13, and 14-17 years). Multigroup confirmatory factor analysis for ordinal responses using weighted least squares estimation evaluated the presence of configural, metric, scalar, and residual invariance. A five-factor model with two within-factor residual correlations provided the best fitting structure. Full metric and residual invariance were supported, while partial scalar invariance was established by freeing item intercepts for "worries," "steals," "restless," and "distracted" in specific age groups. The k-fold cross-validation and the evaluation of the final invariant model in a holdout sample confirmed the robustness of the results. Findings support the use of the SDQ for age group comparisons while highlighting minor violations of MI in adolescence. These results underscore the importance of age-sensitive screening tools and suggest refining SDQ items and response scales to improve developmental risk assessment. (PsycInfo Database Record (c) 2026 APA, all rights reserved).