Neurotrophic factor-related gene polymorphisms and adult attention deficit hyperactivity disorder (ADHD) score in a high-risk male population.

Adult attention deficit hyperactivity disorder (ADHD) is a widely under-reported but nevertheless common condition with a clear heritable component. Several genes have been proposed to play a role in the childhood onset of this neurodevelopmental disorder; however, association studies of persistence of ADHD into adulthood have rarely been performed. Neurotrophic factors (NTFs) are known to be involved in several aspects of neuronal development and neural plasticity in adults. They have also been linked, particularly through brain-derived neurotrophic factor (BDNF) interaction with dopamine transport, to the pathophysiology of ADHD. This study compares the genotypes of six different single nucleotide polymorphisms of genes within the neurotrophin system and their possible association with adult ADHD score in 143 high-risk male subjects referred to a forensic psychiatric unit. The genes included NTF3, NTRK2 (TrkB), NTRK3 (TrkC), BDNF, and p75(NTR). While none of the SNPs showed significant association with ADHD symptoms, one polymorphism within the exon of NTF3 (rs6332) showed a trend toward an association between the A-allele and increased scores using both the retrospective childhood analysis Wender-Utah Rating Scale (WURS-k) (P = 0.05) and the adult ADHD assessment Wender-Reimherr interview (P = 0.03). This SNP is a silent mutation which might be in linkage disequilibrium with a functional risk variant for ADHD. As the association was only suggestive, however, this finding needs replication in a larger study with higher power.