Further, the present study also included data on functional connectivity. To our knowledge, this is the first study to examine associations between white matter and resting state connectivity and FKBP5 genotype. Here, we observed a significant interaction between FKBP5 genotype and PTSD diagnosis; individuals who carried two risk alleles for a putatively functional FKBP5 SNP (rs1360780) and met criteria for a PTSD diagnosis demonstrated relatively poorer cingulum connectivity compared to the other genotype and diagnostic groups. Further, we found that this risk genotype affected functional connectivity at rest. Although statistical power precluded our ability to explore gene by diagnosis interactions in the resting state data, we observed that those individuals who carried two copies of the risk allele demonstrated significantly poorer functional connectivity between the hippocampi and ACC. Remarkably, when cingulum FA was used as a regressor in a seed-based, whole-brain correlational analysis, only the ACC emerged as being functionally coupled with the hippocampus, even after correcting for family-wise error for the whole brain. Similarly, cingulum FA and hippocampal-ACC functional connectivity were found to be highly correlated.
