A single nucleotide polymorphism (SNP) in the PAC1 receptor has been linked to PTSD diagnosis and symptom severity selectively in women (Ressler et al., 2011; Almli et al., 2013; Lind et al., 2017; but see also Chang et al., 2012). The gene discussed is ADCYAP1R1; the disease is post-traumatic stress disorder.