Comparison of LT versus CT PTSD identified overlapping genes with altered expression suggesting enduring markers, while some markers present only in CT PTSD may reflect state measures. As a follow-up, direct comparisons of expression in CT PTSD, LT-only PTSD, and control groups identified FKBP5 and MHC Class II as state markers, and also identified several trait markers. An analysis of indirect effects revealed that homozygosity for any of 4 PTSD risk-related polymorphisms at FKBP5 predicted FKBP5 expression, which mediated indirect effects of genotype on plasma cortisol and PTSD severity. This evidence concerns the gene FKBP5 and post-traumatic stress disorder.