Attention-Deficit/Hyperactivity symptoms in Icelandic schoolchildren: assessment with the Attention Deficit/Hyperactivity Rating Scale-IV.

Four hundred and twenty-seven normal Icelandic children, six and eight years of age, were rated by their parents and three hundred and sixteen children by their teachers with the Teacher and Parent versions of the Attention Deficit/Hyperactivity Disorder Rating Scale-IV (AD/HDRS-IV). For two hundred and sixty-five of the children both parent and teacher ratings were obtained. The factor structures of the AD/HDRS-IV for parents and teachers were in line with theoretical expectations. A Hyperactivity-Impulsivity factor and an Inattention factor were thus well supported. The subscale reliabilities were high. Boys scored higher than girls on all measures and there was a decrease of symptoms with age for boys, as expected. There was evidence of convergent validity for all scales, but discriminant validity of the AD/HDRS-IV subscales is less certain. Generally the instruments seem promising for further research. Some differences are noted in comparison with earlier studies. Thus scores obtained in this study were somewhat lower than those found in American studies, especially for teachers. Also the prevalence of ADHD based on rating scales was lower than in comparable previous studies. The similarity in symptom structure between this and previous studies is emphasized, but the possible role of cultural homogeneity in explaining different results with regard to teachers' ratings of symptoms is suggested.