Attention deficit hyperactivity disorder in children is found to be related to the occurrence of ADHD in siblings and the male gender, but not to birth order, when compared to healthy controls

The aim of the present study was to explore the extent to which the prevalence of attention deficit hyperactivity disorder (ADHD) in childhood is associated with birth order and gender, and the prevalence of ADHD and mental retardation (MR) in siblings, as compared to healthy controls. Methods. Data from 200 children diagnosed with ADHD (mean age: 11.13 years; 10.5% females) were compared to data from 200 healthy controls (mean age: 11.0 years; 27.5% females). The data were related to symptoms of ADHD, birth order, gender, family size, and the occurrence of ADHD and MR in siblings.; Compared to controls, the occurrence of ADHD was found to be related to the male gender and to the occurrence of ADHD-related symptoms in siblings (odds ratio: 13.50). Birth order and MR were not associated with the occurrence of ADHD and ADHD-related symptoms. ADHD- related symptoms increased if a further sibling also suffered from ADHD. Conclusions. Among a sample of Iranian children suffering from ADHD, the ADHD and ADHD-related symptoms in childhood were found to be related to the male gender and to the occurrence of ADHD in siblings. Moreover, birth order was found to be unrelated. The fact that symptoms of ADHD-related symptoms increased if a further sibling was suffering from ADHD, and decreased if a further sibling was suffering from MR, is intriguing and needs further explanation.