Lack of association of polymorphisms in six candidate genes in colombian adhd patients

Background: Attention Deficit and Hyperactivity Disorder (ADHD) is a common childhood neuropsychiatric
condition. The disorder has a multifactorial background, with heritability estimates of around 76%, suggesting
an 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 polymorphisms
was performed using described PCR-based protocols. A TDT analysis was used to test if there was
preferential allelic transmission for any of the six polymorphisms. Additionally, a case-control analysis was
performed 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 patients
with ADHD. There was no evidence of association for any of the studied polymorphic variants in this Colombian
ADHD sample. Further research, with larger sample sizes and study of endophenotypes, is needed
in this population to confirm and extend the results