PDP1 and attention deficit-hyperactivity disorder: The parent-ratings (CBCL) and the teacher-ratings (C-TRF) of the ADHD and PDP-scales were moderately correlated (r = 0.55, p = 0.001 for the ADHD-scales; r = 0.43, p = 0.008 for the PDP-scales) and in all of the following analyses a composite score for the symptom scales calculated as a mean score of the symptom scales of CBCL (rated by parents) and C-TRF (rated by teachers) was used.