A case-control association study of the polymorphism at the promoter region of the DRD4 gene in Korean boys with attention deficit-hyperactivity disorder: Evidence of association with the − 521 C/T SNP

Recent genetic studies at the 5′ end of the dopamine D4 receptor (DRD4) gene have identified several polymorphisms having a possible relationship with attention deficit-hyperactivity disorder (ADHD). This study examined the association between the − 521 and − 376 promoter single nucleotide polymorphisms (SNPs) of the DRD4 gene and ADHD through a case-control association study in Korean boys, who constitute a single ethnic population. Ninety-four ADHD and ninety-five control boys were enrolled in this study. All of the ADHD subjects completed a comprehensive and standardized diagnostic and psychological evaluation battery including the ADHD Rating Scale-IV (ARS). Genotyping for the 2 promoter SNPs was performed. There were significant differences in the genotype and allele frequencies of the − 521 C/T SNP between the ADHD and control groups (χ2 = 6.28, p = 0.043 and χ2 = 6.22, p = 0.013, respectively). However, the distribution of the − 376 C/T genotypes and alleles were similar in the ADHD and control groups. The subtypes of ADHD were not related to either of these two SNPs. In the ADHD subjects, the − 521 TT genotype group had a higher score in the inattentive subscale and a lower score in the hyperactive subscale of the parents version of ARS, although these differences did not attain statistical significance (p = 0.146, p = 0.082). In conclusion, there was a significant association between the − 521 C/T SNP and ADHD in Korean boys. These results suggest a role of the − 521 C/T SNP in the susceptibility for ADHD.