To further explore the role of ADCYAP1R1 in PTSD development and the physiological underpinnings of the stress response, this study examined the main, G × E (rs267735 × trauma exposure), and G × G (with other HPA axis gene polymorphisms) effects of rs2267735 on PTSD severity in a cohort of 2008 Chinese Wenchuan earthquake survivors. The gene discussed is ADCYAP1R1; the disease is post-traumatic stress disorder.