An FKBP5-environment interaction and ADCYAP1R1 have been found to be associated with PTSD (19–22, 28–30), but to our knowledge, few studies have shown a G × G effect of FKBP5 and ADCYAP1R1. Therefore, this is the first study showing that the ADCYAP1R1 polymorphism rs2267735 could affect PTSD development through a novel ADCYAP1R1–FKBP5 interaction. This evidence concerns the gene FKBP5 and post-traumatic stress disorder.