Structural validity and reliability of the Danish self-report Strengths and Difficulties Questionnaire among male and female students in vocational education and training.

Objective: The Strengths and Difficulties Questionnaire (SDQ) is a widely used mental health screening instrument among children and adolescents and increasingly used by welfare professionals in Denmark. However, the psychometric properties of the SDQ-self report (SDQ-S) among vocational education and training (VET) students are unknown. We assess the structural validity, internal consistency reliability, and test-retest reliability of the Danish SDQ-S among these students. Method: The SDQ-S was tested twice in a sample of VET students (sample N = 486; mean age = 17 years) with 10 to 14 days in-between. Using separate analyses for men (n = 371) and women (n = 115), structural validity was assessed using confirmatory factor analysis; internal consistency was assessed using composite reliability (CR); and test-retest reliability using Pearson's correlation. Results: Overall, the results provide inconsistent support for the five-factor first-order model, especially among males. CR was acceptable for all five scales except for Peer problems (among females and males) and Conduct (among males only). Test-retest reliability was satisfactory for all scales among females but for only two of the five scales (Conduct, Hyperactivity) among men. Conclusion: Overall, the SDQ-S is a more valid and reliable instrument among females. Results suggest caution in using the SDQ-S among VET students, in particular males.