The Relationship between Gene SLC6A3 Variable Number of Tandem Repeat (VNTR) and Attention-Deficit / Hyperactivity Disorder

Abbas Seymari; Ashkan  Naseh; Sajjad Rezaei; Zivar Salehi; Maryam Kousha

doi:10.18502/ijps.v19i1.14345

Abbas Seymari Department of Psychology, Faculty of Humanities, Guilan University, Rasht, Iran.
Ashkan Naseh Department of Psychology, Faculty of Humanities, Guilan University, Rasht, Iran.
Sajjad Rezaei Department of Psychology, Faculty of Humanities, Guilan University, Rasht, Iran.
Zivar Salehi Department of Biology, Faculty of Science, Guilan University, Rasht, Iran.
Maryam Kousha Kavosh Cognitive Behavior Sciences and Addiction Research Center, Department of Psychiatry, School of Medicine, Guilan University of Medical Sciences, Rasht, Iran.

DOI: https://doi.org/10.18502/ijps.v19i1.14345

Keywords: Attention Deficit / Hyperactivity Disorder; DAT1 Protein; Gene Polymorphisms; Human; Variable Number of Tandem Repeat

Abstract

Objective: This research investigates the alleles of Variable Number of Tandem Repeats (VNTR) intron 8 of the gene SLC6A3 with attention-deficit / hyperactivity disorder (ADHD) in children and adolescents.

Method: The study’s target population consisted of children and adolescents referred to the specialized clinic, as well as students attending school in Rasht city during 2021-2022. A sample of 95 children between the ages of 6 and 10 with ADHD was selected as the ADHD group, and 95 healthy children were selected as the control group using purposive sampling. The subjects completed the Child Symptom Inventory-4 (CSI-4) checklist after a clinical interview, and demographic information was collected. Genetic sampling was carried out through hair follicles. The sequence of interest was proliferated using the Polymerase Chain Reaction technique )PCR(; afterward, the samples were used for genotype identification on polyacrylamide gel electrophoresis.

Results: The chi-square test results indicated that the 5R / 5R genotype (P = 0.026, χ2 = 7.26) and the 5R allele (P = 0.002, χ2 = 9.35) had a higher frequency compared to the control group. Additionally, the odds ratio test indicated that, compared to other genotypes and alleles, the 5R / 5R genotype (OR = 2.75, 95% CI = 1.29-5.82, P = 0.01) and the 5R allele (OR = 2.02, 95% CI = 1.28-3.19, P = 0.002) increase the odds of developing ADHD by 2.7 and 2 times higher, respectively.

Conclusion: The present study successfully showed the association between intron 8 gene polymorphism, which is responsible for encoding the dopamine transporter as well as ADHD in children and adolescents in Iran.