Association of SNAP-25 Gene Ddel and Mnll Polymorphisms with Adult Attention Deficit Hyperactivity Disorder

Objective The synaptosomal-associated protein of 25 kDa (SNAP-25) gene is a presynaptic plasma membrane protein and an integral component of the vesicle docking and fusion machinery mediating secretion of neurotransmitters. Previously, several studies reported association between SNAP-25 and attention deficit hyperactivity disorder (ADHD). We investigated whether these SNAP-25 polymorphisms (Mnll T/G and Ddell T/C) were also associated with ADHD in the Turkish population. Methods Our study comprised unrelated 139 subjects who met DSM-IV criteria for ADHD and 73 controls and all were of Turkish origin. Genetic analyses were performed and patients were evaluated with Wender-Utah Rating Scale and Adult ADD/ADHD DSM IV-Based Diagnostic Screening and Rating Scale. Results SNAP-25 Ddell polymorphism was not associated with ADHD but there was a statistically significant difference between ADHD patients and controls for SNAP-25 Mnll polymorphism. For SNAP-25 Mnll polymorphism patients with G/G genotype of the SNAP-25 gene Mnll polymorphism had higher Wender-Utah scores and higher scores in the 1st and 3rd parts of adult ADD/ADHD Scale. Conclusion We detected a significant association of the Mnll polymorphism in our ADHD sample which was similar to previous findings. Our study also revealed that SNAP-25 Mnll polymorphism was also associated with symptom severity of ADHD. This study is also, the first report on the association of SNAP-25 with ADHD in the Turkish population.