A case-control association study of serotonin 1A receptor gene and tryptophan hydroxylase 2 gene in attention deficit hyperactivity disorder

Serotonergic system-related genes are likely to be involved in mechanisms underlying attention deficit hyperactivity disorder (ADHD). We investigated the association of serotonin the 1A receptor C-1019G single nucleotide polymorphism (HTR1A C-1019G SNP) and tryptophan hydroxylase 2 gene –703G/T (TPH2 –703G/T) SNP with ADHD.     

Neurotrophin-3 gene,intelligence, and selective attention deficit in a Korean sample with attention-deficit/hyperactivity disorder

Objective

Attention-deficit/hyperactivity disorder (ADHD) is a complex neurodevelopmental disorder with a strong genetic component. Neurotrophin-3 (NTF3), which participates in the differentiation and survival of dopaminergic and noradrenergic neurons, has been identified as a factor in the development of ADHD. We investigated the relationships between ADHD and NTF3 gene polymorphism.

Methods

We conducted a case–control analysis of 202 ADHD subjects and 159 controls, performed a transmission disequilibrium test (TDT) on 151 trios, and compared the intelligence quotient (IQ) and a continuous performance test (CPT) according to the genotype of two single-nucleotide polymorphisms (SNPs) (rs6332 and rs6489630) in the NTF3 gene.

Results

In the case–control and family-based analyses, NTF3 was not significantly associated with ADHD. However, in the ADHD probands, the subjects with AA genotype in the rs6332 SNP had significantly higher mean T-scores for commission errors on the CPT than did those with the AG genotypes (p = 0.045). The mean IQ of the ADHD probands who had the CC genotype of the rs6489630 SNP were higher compared with those who had the CT or TT genotype (p = 0.035). The mean T-score for response time on the CPT was higher in the subjects with TT genotype in the rs6489630 SNP compared to those with the CC or CT genotype, even after adjusting for the effect of IQ (p = 0.021).

Conclusions

These results provide preliminary evidence of an association between NTF3 and the intelligence and selective attention deficit in the Korean population.