Investigation of gene variants predisposing to attention deficit hiperactivity disorder in adults

Attention Deficit and Hyperactivity Disorder (ADHD) is a neuro-developmental disorder characterized by easy distraction, difficulty in maintaining attention, impulsivity, hyperactivity, outbursts of anger, and difficulty in controlling emotions. ADHD is considered to be inherited as a multifactorial inheritance mode in which both genetic and environmental factors play a role in its development. In this tudy, it was aimed to investigate the association/s between DAT1, DRD2, DRD3, DRD4, DBH, HTR2A, and MAOA gene variants and adult ADHD as well as ADHD subtypes. A total of 128 ADHD cases and 100 non-ADHD healthy controls were included in this study. 2ml blood samples were taken from all individuals who were evaluated for psychiatric evaluation. The genotypes for the DAT1, DRD2, DRD3, DRD4, DBH, 5HT2A and MAOA variants were obtained using PCR/PCR-RFLP technique. Statistical analyses were carried out using SPSS program version 20.Genotype and allele frequency P-values were calculated by 2 (2 df)test. To determine any association/s between the eight gene variants and ADHD and the subtypes, statistical analyses were carried out. As a result, no statistical differences were found between the genotype and allele frequencies in ADHD cases versus nonADHD controls cases and controls for seven gene variants studied as well as in terms of subtypes. Only, 4R alelle and 4R/4R genotype of VNTR polymorphism in the DRD4 gene were observed to be the most frequent one in both case and control groups. 4R allele was found to be sttatistically significant in ADHD group than the ones in ontrol group(p=0,01). This suggests that 4R allele might be a risk factor for ADHD in the population studied. In conclusion, a statistically significant association was found only between DRD4 VNTR polymorphism and adult ADHD. However, to confirm that these gene variants contributes to ADHD and ADHD-subtypes, further studies with both higher population sizes and many candidate genes are needed to be investigated simultaneously.