其他摘要：Background Attention deficit hyperactivity disorder (ADHD) is a common behavioral disorder that affects 8-12% of school-age children. Several environmental and genetic factors play a role in the etiology of this disease. One of the genetic factors involved is dopamine beta-hydroxylase (DBH) gene, which plays an essential role in catecholamine synthesis by converting dopamine into norepinephrine. Here we investigated DBH polymorphisms associated with ADHD in North West of Iran. Materials and Methods: This descriptive comparative study was performed on 130 children aged 5-14 years who were diagnosed with ADHD by child and Adolescent psychiatrist following a detailed psychiatric assessment and 130 matching healthy children were also selected from local children’s Hospital in Tabriz city, Iran. Also, 2ml Peripheral blood sample was obtained from all the participants and RFLP-PCR technique was then used to study the polymorphism position rs5320 and allele and genotype frequency of DBH gene. Results: The results showed that the frequency of allele A (as the allele causing the disorder) was 15% in ADHD subjects and 6% in healthy subjects (p
