ADCYAP1 and post-traumatic stress disorder: Ressler et al. demonstrated that PTSD diagnosis was associated with peripheral blood levels of PACAP in females (higher levels in the PTSD cohort), and that an SNP in a putative estrogen response element of the PAC1 receptor gene, rs2267735, was associated with PTSD diagnosis, the severity of symptoms, and with PAC1 receptor messenger RNA expression in the brain.