The Strengths and Difficulties Questionnaire (SDQ) parent-report : bifactor structure and method effects in a community-based sample

Abstract

The Strengths and Difficulties Questionnaire (SDQ) is a widely used screening measure for child mental health, yet findings regarding its latent structure have been inconsistent. The present study examined the structural validity of the SDQ parent-report in a large community sample of mothers of Icelandic children aged 6–12 years (N = 2332). Competing measurement models were evaluated, including the original five-factor structure, second-order and bifactor models, estimated with and without a method factor capturing covariance among positively worded items. Model comparisons indicated that a bifactor model including two broad general factors—Externalizing and Internalizing problems—together with a Prosocial Behavior factor and an orthogonal wording-related method factor provided the most interpretable representation. The Externalizing (ωH = 0.69; ECV = 0.65) and Internalizing (ωH = 0.58; ECV = 0.55) factors accounted for a substantial proportion of reliable variance among the symptom-based items, whereas the specific SDQ factors, particularly Conduct Problems and Peer Problems, contributed relatively limited variance beyond these broader factors. The wording method factor accounted for a notable share of covariance among positively worded items, particularly those from the Prosocial Behavior domain, consistent with structured wording-related variance. Sensitivity analyses using alternative specifications, including exploratory structural equation modeling and a random-intercept factor approach, yielded converging results. The findings highlight the influence of wording-related covariance and skewed and restricted response distributions, underscoring the importance of accounting for these sources of variance when interpreting SDQ scores. Broad Internalizing and Externalizing scores may therefore provide more stable indicators of child mental health difficulties in non-clinical populations.