A primary limitation of the present study is the sample size, which is likely to have reduced power to detect between-group differences in resting state connectivity and associations with FKBP5 genotype. We chose to restrict our analyses to the cingulum, given that this tract has demonstrated associations with cognitive and affective features that characterize PTSD (9, 53); however, it is possible that connectivity of other white matter tracts, including the corpus callosum and fornix, would be relevant to these phenomena. Further studies that examine other promising tracts of interest are certainly warranted to establish the presence of other intermediate neural phenotypes for PTSD. Further, the sample size was small for genotype by diagnosis analyses, which raises the possibility of false positive findings; thus, replication is warranted with a larger sample size.
