Age-specific norms and validation of the German SDQ parent version based on a nationally representative sample (KiGGS).

The Strengths and Difficulties Questionnaire (SDQ) is the most widely used mental health screening instrument for children and adolescents. It is a short questionnaire including 25 items that can be answered by parents, teachers or children. There are two studies which report norms for the German SDQ parent version. They do not include children younger than 6 years. Moreover, whether the German SDQ parent version is measurement invariant across age has not yet been investigated. The absence of measurement invariance across age would support the use of age-specific norms that are not yet available for the German SDQ parent version. We used data of the German Health Interview and Examination Survey for Children and Adolescents (KiGGS), a nationally representative survey including 14,835 children aged 3-17 years, to assess measurement invariance of the German SDQ parent version across the full age range. Multi-group confirmatory factor analysis revealed that the hyperactivity and emotional symptoms subscales are not comparable between children of different ages. This supports the use of age-specific norms for these two subscales and for the total SDQ. We used methods of centile estimation to smoothly model the centiles of the SDQ total score and the subscale scores in dependence on age. These age-specific centiles reflect the developmental course of SDQ problems in children (including preschoolers) and adolescents living in Germany. They can be used to identify children and adolescents with abnormal behaviour, while accounting for the developmental course of emotional and behaviour problems.