Analysis of molecular changes in DRD4 Gene Polymorphism in children with Attention Deficit Hyperactivity Disorder in relation to the response to treatment with Methylphenidate

Abstract

ADHD (Attention Deficit Hyperactivity Disorder) is one of the most frequent psychiatric disorders in school-aged children. ADHD is strongly rooted in the genetic background and various factors contribute to its etiology. Relevant studies provide contradictory results. Thus, present research aims to determine the relationship between DRD4 gene polymorphism and response to methylphenidate treatment. Materials and Methods: Present descriptive-analytic research was conducted on 5-18 years old children with ADHD in Tabriz city during 2017. Patient with ADHD were included in the study through a clinical interview based on DMS-IV-TR criteria with parental consent. In addition to demographic questionnaire, also a semi-structured diagnostic instrument, i.e. K-SADS and ADHD Parent Rating Scale were respectively used to distinguish ADHD children from control group and inattention symptoms from hyper activity and impulsivity symptoms. After completion of questionnaires, 4 ml of blood was taken from each patient and DNA was extracted using salting out technique. Eight weeks after starting treatment with methylphenidate (Ritalin®), symptom intensity was measured for the second time using Conners’ rating scale. Response to treatment was determined based on changes in scores. Finally all data collected from questionnaires and laboratory tests were analyzed statistically using relevant software. Results: Present research was conducted on a sample of 140 children with ADHD among them 118 ones (84.3) were male and others were female. The average age of patients was 9.05 ± 2.88 years. The average scores obtained from ADHD rating scale and Conners’ rating scale before starting the study were 28 ± 11.96 and 44.98 ± 16.98 respectively. In present research 16 children (11.4%) had a DRD4 mutant subtype. Also the DRD4 subtype with a 700bp exon was found in 110 children in the sample (78.6%) representing the most common form of DRD4 subtype. It was found that symptom intensity decreased significantly after methylphenidate prescription. However no relationship was found between the extent of decrease in symptom intensity and DRD4 mutations.