Background: Attention Deficit and Hyperactivity Disorder (ADHD) is a common childhood neuropsychiatriccondition. The disorder has a multifactorial background, with heritability estimates of around 76%, suggestingan important role of genetic factors. Candidate genes include those related to dopaminergic (e.g.DRD4, DRD5, SLC6A3 and DBH)and serotoninergic (e.g.HTR1B and SLC6A4) pathways.Purpose: To explore the association of common polymorphisms in six genes (DRD4, DRD5, SLC6A3, DBH,HTR1B and SLC6A4) and the susceptibility to ADHD in a Colombian sample population.Methods: Eighty-six ADHD trios and 152 healthy controls were recruited. Genotyping of the six polymorphismswas performed using described PCR-based protocols. A TDT analysis was used to test if there waspreferential allelic transmission for any of the six polymorphisms. Additionally, a case-control analysis wasperformed to test for association of the serotoninergic (HTR1B and SLC6A4) polymorphisms with ADHD.Results: Through the TDT analysis there was no preferential allelic transmission for any of the studied variants.Case-control analysis did not show association.Conclusion: This is the first study in Latin America to describe six polymorphisms in a group of patientswith ADHD. There was no evidence of association for any of the studied polymorphic variants in this ColombianADHD sample. Further research, with larger sample sizes and study of endophenotypes, is neededin this population to confirm and extend the results
