SNP-SNP interactions in the BDNF, COMT, CBR1 and CCK genes, associated with post-traumatic stress disorder in urban residents of Itagüí, Colombia

Introduction: Single nucleotide polymorphisms (SNPs) in the BDNF , COMT , CBR1 and CCK genes have been associated with the process of fear extinction in humans. Since fear extinction plays a key role in recovering from psychological trauma, there is a possibility that these genes modulate the risk of developing posttraumatic stress disorder (PTSD). Objective: To assess unilocus and multilocus associations between SNPs in the BDNF , COMT , CBR1 and CCK genes and the risk of developing PTSD. Materials and methods: 129 inhabitants of the municipality of Itagui, Colombia, who had experienced psychological trauma at least once, were genotyped for these polymorphisms (38 cases of PTSD and 91 controls). Logistic regression was used to perform unilocus and multilocus association tests for single SNPs and existing SNP-SNP genotypic combinations. Results: No unilocus associations were found, but interactions between the BDNF and CBR1 genes and between the COMT and CCK genes were observed. Of these interactions, the genotypic combinations that behaved as risk factors were AG-AA (OR=13.52, p<0.05) in the BDNF - CBR1 interaction, and TC-AA (OR=13.70, p<0.05) in the CCK-COMT interaction. Conclusions: The two pairs of interacting polymorphisms found in this study could act additively and generate a greater risk of developing PTSD after suffering psychological trauma. People who have a single allele have a lower risk of developing PTSD than those who have two alleles in the interacting genes.