Child ADHD and child ODD (cADHD, cODD)

Child symptoms of ADHD and ODD were each assessed independently by a clinician and by the parents. For the assessment of ADHD symptoms, the clinician used the 18 items of the German Diagnostic Checklist for ADHD (DCL-ADHS, DISYPS-III; [17], which reflect the criteria for ADHD according to the DSM-5 and the 10th edition of the International Statistical Classification of Diseases and Related Health Problems (10th ed.; [59]). For the assessment of oppositional symptoms, the clinician used the eight ODD items from the German Diagnostic Checklist for Oppositional Defiant and Conduct Disorder (CD) (DCL-SSV, DISYPS-III; [17]), which reflect the criteria for ODD according to the DSM-5 and ICD-10. The symptoms were explored using a German semi-structured clinical interview for ADHD, ODD and CD symptoms, which was conducted with at least one parent (ILF-EXTERNAL, DISYPS-ILF, [26]). Clinicians rated each item on a 4-point Likert scale ranging from 0 (age-typical/not at all) to 3 (very much, with higher scores indicating more pronounced child ADHD and ODD symptoms. The two scale values (ADHD, ODD were formed by averaging the respective item scores. In the present sample, the scales showed a good internal consistency (ADHD: α = 0.82; ODD: α = 0.83). Furthermore, a high interrater reliability has been reported, with an intraclass correlation of 0.91 (ADHD) and 0.94 (ODD) [57].

The parents assessed the children's ADHD and ODD symptoms using the German-language rating scales for ADHD (FBB-ADHS) and for ODD and CD (FBB-SSV, DISYPS-III; [17]), which are based on the DSM-5 and ICD-10. More specifically, parents rated 20 ADHD items (nine items on inattention, 11 items on hyperactivity) and eight ODD items on a 4-point Likert scale ranging from 0 (not at all) to 3 (markedly), with higher scores indicating more severe symptoms. Again, the two scale values (ADHD, ODD) were formed by averaging the respective item scores. In the present sample, the scales showed a good internal consistency, with a Cronbach’s alpha of 0.89 for each scale.