NR3C1 and post-traumatic stress disorder: Several biological parameters have already been found to predict PTSD treatment response, for example: cytosine methylation; GR gene expression; 5-HTTLPR genotype; BDNF in serum; anterior cingulate cortex (ACC) volume and ACC and amygdala activity (for review, see Thomaes et al., 2014; Yehuda et al., 2013).