Conversely, no significant associations were detected for the HTR1B (rs6296) and the other HTR2A (rs6311, rs6313) polymorphisms.<h4>Conclusions</h4>These findings suggest that genetic variations in the serotonergic system, particularly within the HTR2A gene, may contribute to the genetic susceptibility to ADHD. Here, HTR2A is linked to attention deficit-hyperactivity disorder.